Last year the old man____ under the roof ,enjoying the sunlight A.sits B .is sitting C .sit

Last year the old man____ under the roof ,enjoying the sunlight A.sits B .is sitting C .sit
D.would sit
1.Last year the old man____ under the roof ,enjoying the sunlight A.sits B .is sitting C .sit D.would sit
2.We _____ each other when we studied together .
A .helping B .are helping C .would help D .do help
3.Though we pushed the car hard ,the car ____ away .
A.wouldn't move B .moved C .would move D .doesn't move
这三道题我都解释不出来应该选什么，