1. I am busy studying for the mid-term exam.
2. I am busy studying for the midterm exam.
3. I am busy studying for the mid-term exams.
4. I am busy studying for the mid-term exams.
(Here in our country, During the period of the mid-term exam(s), students have tests for all the subjects, about 10 subjects. So they have to prepare for all the tests. In this case which expressions are grammatical?)
3 and 4 are the same and are correct for the multiple-exams situation you described.
All of the expressions you provided are grammatical.
1. "I am busy studying for the mid-term exam." This suggests that there is a single mid-term exam that you are studying for.
2. "I am busy studying for the midterm exam." This is similar to the first expression and suggests that there is a single midterm exam.
3. "I am busy studying for the mid-term exams." This indicates that you have multiple mid-term exams for different subjects.
4. "I am busy studying for the mid-term exams." This is the same as the third expression and suggests that you have more than one mid-term exam to prepare for.
All of these expressions are correct and understandable, but the choice between using "midterm" (without a hyphen) or "mid-term" (with a hyphen) is a matter of style and personal preference.
All four expressions are grammatically correct. The difference lies in the use of "exam" versus "exams" and "mid-term" versus "midterm."
1. "I am busy studying for the mid-term exam." - This implies that you have one specific mid-term exam that you are studying for.
2. "I am busy studying for the midterm exam." - This also implies that you have one specific midterm exam that you are studying for. The term "midterm" is often used as a single word in certain contexts.
3. "I am busy studying for the mid-term exams." - This suggests that you have multiple mid-term exams that you are studying for, possibly for different subjects.
4. "I am busy studying for the mid-term exams." - Similar to the previous expression, this indicates that you have multiple mid-term exams that you are preparing for.
Based on the information you provided, expressions 3 and 4 seem more appropriate because you mentioned that students have tests for all subjects during the mid-term exam period.