I urgently need you to answer this question:

1) Is class the American English for lesson?
Because students are asked to choose among three alternatives (one must be correct): a) lesson b) subject c) course
If your next ....... is chemistry, physics or biology, go to the labs (1st floor).

The only choice that would work is "subject" I guess. I'd use class, and that may be the American English word. If you are studying British English, then I'm not sure, but "subject" seems best.

To me ...

... lesson is a particular sub-topic being taught by a particular subject's teacher on any given day. Some teachers give more than one lesson during one particular classtime.

... subject is the discipline being studied (English, Italian, math, science, business...), but it's be best fit for your sentence if "class" is not a choice.

... course is the name of the class within the discipline. For example, in the broad discipline of Latin, there could be these courses: Latin I, Latin II, Caesar's Gallic Wars, Vergil's Aeneid, Cicero's Speeches, Medieval Latin, etc.

should be: ... but it's the best fit ...

Yes, in American English, the term "class" is often used as a synonym for "lesson." However, it is important to note that the context is crucial in determining the correct interpretation of a word. In the given sentence, students are asked to choose among three alternatives, which are "lesson," "subject," or "course." To determine the correct answer from these options, we need to consider the next part of the sentence.

The sentence mentions that if your next __________ is chemistry, physics, or biology, go to the labs on the 1st floor. From this information, we can infer that the missing word is related to specific subjects being taught.

Based on this context, the correct answer would likely be "subject." This is because the phrase "next subject" refers to the upcoming class or lesson that a student will have. Therefore, in this context, "subject" is the most appropriate option among the three alternatives provided.