He earned enough money to start his own business offering guide services tourists.A. by;

问题补充：

He earned enough money to start his own business offering guide services tourists.

A. by; to

B. with; at

C. on; for

D. through; with

答案：

(答案→)A. by; to

B. with; at

C. on; for

D. through; with

解析：介词by可以表示手段、原因，常置于动名词前，如：You can make the cake by mixing eggs and flour. 其次考查介词与动词offer的搭配，offer sth. to sb. = give sth. to sb.其中的to表示对象。