B

1.He didn't realize how talented he was until he started work

=>only when

2. they had hardly been reunited when they were deep in conservation about the past

=>hardly

3.you won't find a school anywhere whose pupils get such good results

=> nowhere

Đảo ngữ

1.we don't know how the twins feel about each other until they have met for the first time.

=>not until

2.Such research has never been carried out before

=>never before

3.you seldom find reunited twins who don't get on well together

=>seldom

4.evens scarely left school before he found a job in a computer software

=>sacrely