【简答题】塑料的主要成分是________,热塑性塑料的特点是_______ ,热固性塑料的特点是______。 人们根据需要制成了许多特殊用途的塑料,如________塑料、_______塑料、________塑料等,其中_________塑料在宇宙航空、原子能工业和其他尖端技术领域将发挥重要的作用。
【单选题】What is the main problem?
A.
He doesn't know what color his friend likes in a gift.
B.
His friend has a broken knapsack.
C.
The gift he wants isn't there.
D.
He doesn't know what his friend will find useful in a gift.
【单选题】In the ________ of the race between the tortoise and the hare, the tortoise wins, even though he is slow, because he keeps going with determination.
【判断题】设置会计科目非常重要,是编制会计报表的基础。 ( )
【判断题】T he tortoise is friendly. ( )