1 You should listen to your teacher in class with_care__.(with 后面用名词小心,细心） _carefulness__is nececcary in listening to your teacher in class.（carefulness指细心这个品质）
A care B carefulness
2 However _difficult___it is,you must finish it in time.（这是一个倒装句式,应该在it is 后面,用形容词
Whatever _difficulty___you meet,you must finish it in time
.（这是一个倒装句式,应该在you meet后面,用名词
A difficult B difficulty