You can only be sure of __________ you have at present; you cannot be sure of something __________ you might get in the future.

A. that; what   B. what; / C. which; that   D. /; that

It was along the Mississippi River ______ Mark Twain spent much of his childhood _____ the story happened.

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

It ____in this new hall ____ was just set up last month ________ we held an important meeting yesterday.

. It is exactly      we behave          has changed the world.

A．which; that                 B．how; that             C．how; what           D．what; that

The most important thing ______ we should consider is the first idea _____ he has mentioned in the speech.