— Hi, Lydia. Are you going to the concert on Friday?  

— I'd like to . But there are so many problems_____.[ ]

A. remained to be settled

B. remaining to be settled

C. remained settled

D. remaining settled

马氏体的塑性和韧性与其含碳量有关，（）状马氏体有良好的塑性和韧性。