هام قبل ان يقع طلابكم فى الخطأ

[as seif]

It is very difficult for enough context to be given to make the choice completely clear, especially in a test where students are just looking at a sentence. I think that there is enough information to choose correctly in these cases as long as the students follow the grammar rules in the Student's Book exactly. I agree that it is not easy though.

If we have need to and must among the options need to is better. However, if we have only must in the options, it is 100 % correct. الف شكر لكم جميعا على هذا البحث وهذه المناقشه المفيده...mr.mahrous...mr.omar...