1. Exactly _____ the potato was introduced into Europe is uncertain, but it was probably around 1565.

  A. how            B. why                  C. when                 D. whether

2. LiHua stepped outside his front door to see _____ the weather was like.

  A. that           B. what             C. how                  D. when

3. I am delighted at the news _____ we will spend our holiday in Hainan.

A. that           B. which            C. what             D. when

4. That evening, _____I will tell you later, I ended up with working very late.

  A. when           B. as               C. which            D. what

5. His brother works in a factory _____ name always appears in the local newspaper.

A. where              B. which            C. that                 D. whose

6. We’ll reach the sales goal in a month _____we set at the beginning of the year.

A. when           B. what             C. which            D. why