----enough sleep before takong a test will improve your ment

____enough sleep before takong a test will improve your mental alertness so you can think clearly.
A Getting B That get C Get D Got(什么时候在可以前面加上that作为句子的主语呢?）
2.It's not an easy job such a littke boy to go up the stairs ____a bag of books.
A to carry B carried C carrying D having carried(为什么不选A?,选C和选D的区别）
详细解析一下!Thanks you!~