Multiple Choice:

1. Mathematics.......... is not always an exact science.
   Answer: c. is

2. Mr. John, accompanied by several members of the committee,.......... has proposed some changes of the rules.
   Answer: b. has

3. If it had rained two hours ago, the streets... would be wet now.
   Answer: d. would be

4. If I... to the park last weekend, I would be tired today.
   Answer: c. had gone

Exercise 2: Rewrite Sentences

1. I am not rich. I didn’t buy a new car last month.
   ➔ If I were rich, I would have bought a new car last month.

2. We can’t reach Tom’s house now because we didn’t ask for directions before.
   ➔ If we had asked for directions before, we could reach Tom’s house now.

3. My grandfather wishes he could live in Danang with us.
   ➔ If only my grandfather could live in Danang with us.

1. Mathematics.......... not always an exact science.
   Đáp án: c. is
   Giải thích: "Mathematics" là danh từ số ít, nên động từ phải dùng "is".

2. Mr. John, accompanied by several members of the committee,.......... proposed some changes of the rules.
   Đáp án: b. has
   Giải thích: Dù có "several members", chủ ngữ chính vẫn là "Mr. John", nên động từ phải là "has".

3. If it had rained two hours ago, the streets... wet now.
   Đáp án: D. would be
   Giải thích: Đây là câu điều kiện loại 3 (nói về điều kiện không có thật trong quá khứ), kết quả là điều kiện loại 2 (diễn tả điều không có thật trong hiện tại).

4. If I... to the park last weekend, I would be tired today.
   Đáp án: C. had gone
   Giải thích: Đây là câu điều kiện loại 3 (nói về một hành động không xảy ra trong quá khứ, kết quả của nó ảnh hưởng đến hiện tại).

Rewrite the following sentences using conditionals:

1. I am not rich. I didn’t buy a new car last month.
   => If I were rich, I would have bought a new car last month.

2. We can’t reach Tom’s house now because we didn’t ask for directions before.
   => If we had asked for directions before, we could reach Tom’s house now.

3. My grandfather wishes he could live in Danang with us.
   => If only my grandfather could live in Danang with us.