When ____ about the source of his income, he hesitated for a moment, obviously not willing to give us a direct answer.

The monument was built in honor of the explorer who was believed＿＿the big river.

 China's first moon rover, Yutu, or Jade Rabbit touched the lunar surface at 9:14 a.m.on December 14,2013,  ________deep trace on the loose lunar soil.

____by one of his fellow soldiers，the wounded man walked slowly across the field．

 “How do you deal with the disagreement between the company and the customers?” “The key ______ the problem is to meet the demand ______ by the customers.”