Choose the sentence which has the closest meaning to the original one.I don’t know the answer, so I can’t tell you.
A.If I know the answer, I will tell you.
B.If I had known the answer, I would have told you.
C.If I knew the answer, I will tell you.
D.If I knew the answer, I would tell you.

If the tree weren’t so high, he could climb it up to take his kite down.
A.The tree is so high, he can’t climb it up to take his kite down.
B.
C.The tree isn’t so high, he could climb it up to take his kite down.
D.The tree wasn’t so high, could climb it up to take his kite down.

If you had driven more carefully, we wouldn’t have had that accident.
A.
B.Were you to drive more carefully, we wouldn’t have that accident.
C.Had you driven more carefully, we wouldn’t have had that accident.
D.Had you driven more carefully, we would have had that accident.

He had all the necessary books he doesn't use them to study.
A.Because he had all the necessary books, he doesn't use them to study.
B.Now that he had all the necessary books, he doesn't use them to study.
C.Even though he had all the necessary books, he doesn't use them to study.
D.Although he had all the necessary books, but he doesn't use them to study.

I forgot to keep the milk in the refrigerator, so it went bad.
A.The milk went bad because I forgot to keep it in the refrigerator.
B.
C.The milk went bad until I forgot to keep it in the refrigerator.
D.The milk went bad yet I forgot to keep it in the refrigerator.

His father died at a young age, so he had a difficult childhood.
A.He had a difficult childhood so that his father died at a young age.
B.He had a difficult childhood because of the fact that his father died at a young age.
C.He had a difficult childhood owing to his father died at a young age.
D.He had a difficult childhood though his father died at a young age.

The air in the city is polluted, but people like to live there.
A.People like to live in the city despite the air is polluted.
B.People like to live in the city though the air is polluted.
C.People like to live in the city seeing that the air is polluted.
D.People like to live in the city but the air is polluted.

He gave me his address. He wanted me to visit him.
A.He gave me his address so that I would visit him.
B.He gave me his address because I would visit him.
C.He gave me his address though I would visit him.
D.He gave me his address yet I would visit him.

I did not want to hear what they were talking about, which is why I put the music louder.
A.I put the music louder in order to not hear what they were talking about.
B.I put the music louder although I didn’t want to hear what they were talking about.
C.I put the music louder but I didn’t want to hear what they were talking about.
D.I put the music louder so as not to hear what they were talking about.

Cars cause pollution but people still want them.
A.Because cars cause pollution, people want them.
B.
C.Cars cause pollution although people want them.
D.Cars cause pollution because people still want them.