问题

_______,I lost heart in English learning,but my teacher often said to me,”Keep on working hard; you’ll succeed________.”[ ]
A: At a time; in time
B: At a time; on time
C: At one time; in time
D: At one time; on time
B: At a time; on time
C: At one time; in time
D: At one time; on time
正确答案是: