1 C had exploded 2 A phoned
3 She will know the answer if she tries to understand. (точно ошибка в С - не try, а tries, но вот в D я бы поставила инфинитив to understand вместо understanding, но раз в предложении только одна ошибка, то оставьте только вариант C)
4 D most popular
5 C hitting
6 A to drive
7 If he had been careful he wouldn't have had that terrible accident. (в этом предложении be вообще не в тему, не пойму, зачем оно стоит)
8 If she had taken care of her son he wouldn't have become a criminal
9 The relationship between tourism and criminal have been long noted.
1 has been raining
2 sold
3 has been smoking
4 had been driving
5 hasn't gone
6 had lost
7 has written
8 has known
9 entered, had already begun
10 have had