French

Another question,
for example, la Chine, le Japon,
we use en (preposition) for feminine countries = en Chine
masculin = au Japon
I was also told that for l' such as l'Allemagne, we use "en".
But what about l'Iran, since it is l' but Iran is also masculine. Do i use en or au?

Salut et bonne question! Geographical expressions can indeed cause difficulty!

The definite article is used with names of countries, continents, provinces, rivers and mountains, BUT NOT with names of cities: (generally)

Il a visité la France et l'Italie.
Nous partons pour l'Europe.
La Normandie est une belle province.
Bruxelles est la capitale de la Belgique.
Avez-vous vu les Alpes?
Paris est sur la Seine.
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PREPOSITIONS WITH PLACE NAMES
To express "to" or "in" with place names:

en + feminine countries, continents, provinces = en France, en Europe, en
Bretagne

au, auz + masculine countries = au Canada, aux Etats-Unis

à + cities = à Londres

Je désire aller en France = I want to go to France.

Elle demeure au Canada = She lives in Canada.

Resterez-vous à Londres? = Will you stay in London?

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To express "from" with place names:

de + fewminine, countries, continents, provinces = de France, d'Europe, de Bretagne

du, des + masculine countries = du Canada, des Etats-Unis

de + cities = de Londres

Ces enfants viennent de France et du Canada. = These children come from France and Canada.

Ils sont arrivés de Londres. = They arrived from London.

NOTE: 1. With masculine countries, the definitre article is always used.

2. With modified continents, the prepositions are as follows:

l'Amériqe du Nord (North America)
to, in: dans l'Amérrique du Nord
from: de l'Amérique du Nord

l'Amérique du Sud (South America)
to, in: dans l'Amérique du Sud
from: de l'Amérique du Sud

3. A few cities always have a definite article in French, since the article is part of the name:

le Havre, Havre
to, in: au Havre
from: du Havre

la Nouvelle-Orléans
to, in: à la Nouvelle-Orléans
from: de la Nouvelle-Orléans
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FEMININE COUNTRIES, CONTINENTS, PROVINCES

l'Allemagne = German
l'Angleterre = England
la Belgique = Belgium
la Chine = China
l'Espagne = Spain
la France = Francew
l'Italie = Italy
la Russie = Russia
la Suisse = Switzerland

l'Afrique = Africa
l'Amérique = America
l'Asie = Asia
l'Europe = Europe

l'Alsace = Alsace
la Bourgogne = Burgundy
la Bretagne = Brittany
la Champagne = Champagne
la Lorraine = Lorraine
la Normandie = Normandy
la Provence = Province

MASCULINE COUNTRIES

le Canada = Canada
le Danemark = Denmark
les Etats-Unis = the United States
le Japon = Japan
le Mexique = Mexico
le Portugal = Portugal

RIVERS AND MOUNTAINS

la Garonne = the
Gar4onne River
la Loire = the Loire
le Rhin = the Rhine
le Rhône = the Rhone
la Seine = the Seine

les Alpes (f.) = the Alps
le Jura = the Jura Mountains
les Pyrénées (f.) = the Pryrenees
les Vosges = the Voges Mountains
le mont Blanc = Mount Blanc

Mme

P.S. I nearly missed your 2nd question.
l'Allemagne = feminine = en Allemagne
l'Iran = masculine, beginning with a vowel = en Iran

Some things to add to the previous explanation:

en + feminine countries, continents, provinces
*** en + masculine singular countries beginning with a vowel = en Iran, en Israël, en Iraq

NOTE: 1. With Danemark and Portugal, either "au" or "en" may be used. = au Danemark OR en Danemark / au Portugal OR en Portugal
2. In current French, the use of "dans" with modified feminine place names is gradually decreasing. "En" is retained when the modifier is an integral part of the place name, and usually when a modifying adjective follows the name = en Amérique du Sud / en Suisse italienne / en Asie Mineure / en Europe occidentale

In other cases, dans + definite article are used = dans la douce France / dans l'Italie de la Renaissance

3. With names of cities, "dans" may be used instead of "à" to stress the idea of "inside" or "within" the city = dans Lyon, dans Bruxelles
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from:
de + feminine countries, continents, provinces
***de + masculine singular countries beginning with a vowel = d'Iran, d'Israël, d'Iraq

NOTE: 1. The definite article with modified feminine place names is becoming less frequent after "de." It is generally dropped when the modifier is an integral part of the place name or when a modifing adjective follows the name = d'Afrique du Nord / de Russie centrale

Mme