A:yyRr×YYrr
B:yyRr×Yyrr
C:YYRr×yyRr
D:yyRR×Yyrr
据图中内容,可以推断的是_________在位期间的社会状况。( )
Fire is very important ________ we need to use it to cook food.
I haven't seen _______ this since I began to collect stamps.