几天过去了，你对这一类词掌握得如何呀？本天是对前几天的一个复习，古人云：温故而知新。不要放弃任何一个小小的挑战哟！
1. A. This plane is in the （过程）of the flight.
B. What’s the （原因）of the accident?
C. Where is the （源头）of the river?
2. A. Many （式样）of bicycles are on show.
B. Fill in the blanks with proper （情态的）verbs.
