“Tom went on painting.” 请问为什么在介词on之后,动词paint还要加“ing"?

“Tom went on painting.” 请问为什么在介词on之后,动词paint还要加“ing? went on Tom used to went to school by bus on his own 改错 Tom used to went to school by bus on his own 改错 Tom used to went to school by bus on his own 改错 急 Tom and his friends went boating on the l( ) yesterday afternoon填什么? 英语翻译Tom's happy smile was back on his face.It went from ear to ear. where did tom go_______vacation?He_____themoutains.A.to;goes to B.on;went to C.on;goes to After Tom finished the kite,he went on ___ it.A.flying B.fly C.flies D.to fly went on went over went down went out on and on they went. went on a went on with Tom went to see a doctor q___ tell me when tom went to Tom went home and t__hard about it Tom,__bicycle I went to the concert ,is a friend of mineA.whom B.who C.whose D.on whose为什么选D, we went on the trip to suzhou----tom because he was ill.A besidsB withC exceptD of选哪个,为啥呢,请赐教