2. If you swim in a river or lake, be sure to investigate ________ is below the water surface. Often there are rocks or branches hidden in the water. (浙江2015)

3. -I wonder ________ Mary has kept her figure after all these years.

　-By working out every day. (福建2015)

4. You have to know ________ you're going if you are to plan the best way of getting there. (湖南2015)

【点拨】

1. that。设空处引导宾语从句，且从句结构及意义均完整，故填that。

2. what。设空处引导宾语从句，在从句中作主语，且由Often there are rocks ... in the water可知，设空处指物，故填what。

3. how。设空处引导宾语从句，且由By working out every day可知，设空处表方式，故填how。

4. where。设空处引导宾语从句，且由plan the best way of getting there可知，设空处表地点，故填where。

考点三：表语从句

【考例】

用适当的连接词填空。

1. A ship in harbor is safe, but that's not ________ ships are built for. (安徽2015)

2. The best moment for the football star was ________ he scored the winning goal. (北京2014)

【点拨】

1. what。设空处引导表语从句，且在从句中作for的宾语，故填what。

2. when。设空处引导表语从句，且由The best moment可知，设空处表时间，故填when。

考点四：同位语从句

【考例】

用适当的连接词填空。

1. -Is it true that Mike refused an offer from Yale University yesterday?