Yesterday I helped Tom -------- his radio. 为什么--------要选mend

Yesterday I helped Tom -------- his radio. 为什么--------要选mend i helped Tom finsh his lessons对吗? he helped me mend the bike yesterday,yesterday修饰什么 yesterday I helped him__the homework I notice Tom ＿his homework yesterday横线上填do的什么形式?为什么? I helped Tom buy 还是I helped Tom bought I helped him find his father.为什么find不用过去式? i got my bike ＿ yesterday.为什么填mended,mend哪错了 Tom hurt his leg yesterday为什么不是hurted? It was my grandfather _____ helped mike mend his bike this m I helped Tom bought a new computer. Mike yesterday helped his the father wash car