A:grapefruit
B:watermelon
C:apple
D:water bottle
— I didn't see you yesterday.
— ______ I was ill yesterday, ______ I didn't go to work.
1988年,我国发行了一套《中国现代科学家》纪念邮票,这套邮票共4枚,《地质学家——李四光》就是其中一枚。李四光能够享有这样的荣誉,主要是因为( )