1. A: Where can we hear this announcement?

B: We can here it in an airplane.

2. A: Where can we hear this announcement?
B: We can here it on an airplane.

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Q1: Do we have to use 'in' or 'on'?
Q2: Is the expression 'announce' (from athe pilot) correct?

In or on are both correct. If you are ONboard an airplane, you are IN the airplane. And "announcement" is correct.

B: We can here it in an airplane.

should be

B: We can hear it in an airplane.

To answer your questions:

Q1: When talking about hearing announcements on an airplane, it is more commonly correct to use the preposition 'on' instead of 'in.' So, the correct response would be "We can hear it on an airplane."

Q2: The correct verb to use in this context would be 'hear' instead of 'announce.' The announcement is made by someone (like a pilot or flight attendant) and is heard by the passengers. So, the correct expression would be "We can hear the announcement on an airplane."

To determine these answers, you can consider the following:

1. Context: Think about the situation in which the announcement is being made. In this case, it is on an airplane, as the announcement is specifically related to something happening during the flight.

2. Grammatical rules: In English, we use prepositions like 'on' or 'in' to indicate the location or position of something. When it comes to transportation, 'on' is commonly used to indicate being on board or experiencing the vehicle, like an airplane.

3. Usage and common phrases: By observing how native English speakers commonly refer to hearing announcements on airplanes, you will notice the phrase "hear it on an airplane" is more frequently used.

Similarly, when considering the verb used for the announcement, you can analyze who is responsible for making the announcement and who is receiving it. In this case, it is the pilot or flight attendant making the announcement, and passengers are receiving it, so the correct verb is 'hear.'

It's essential to understand the context, follow grammatical rules, and recognize common phrases to answer such questions accurately.