问题补充：
Bill is not a fast runner and he doesn have a chance of winning the marathon, but he will the race even if he finishes last.
A. keep on
B. keep to
C. stick out
D. stick to
答案：
A. keep on
B. keep to
(答案→)C. stick out
D. stick to
解析：stick out(=keep on doing sth。until it is done，no matter how long，hard，or unpleasant) 坚持下去: Mathematics is hard，but if you stick it out you will understanding it(=Mathematics is hard，but if you keep on working hard at it you will learn it.) 此外，stick on 还可表示 (stand out) 突出: The skyscraper sticks out against the bkue sky.(这幢摩天大楼映着蓝图显得格外突出.)
[注意] stick out与keep to 均有“坚持”的含义。stick out 特指“坚持下功夫干一件事，不完成决不收兵”；而keep to 则强调“坚持、遵守、坚守”诺言、规则、原则、精神、岗位。可见，keep to 的英文释义为 ability by；adhere to，stick closely to。例如: keep to ones promise(遵守诺言)；keep to the rules of a game(遵守比赛规则)；keep to a principle(坚持原则)；keep ones pos(坚守岗位)。因此，我们可以说keep to相当于 stick to，而区别于 stick out.
