英语高手请进.请写出过程和原因.----为横线1.The old man often hears programmes

英语高手请进.
请写出过程和原因.----为横线
1.The old man often hears programmes ---- the radio.
A.on B.of C.from D.from D.by
2.There is a watch tower ----[警告] swimmers about sharks.
3.He ----[证明] himself to be an outstanding soldier.
4.My grandparent live in a village ----[在.之中]the hills.
5.We met the hero at the ----[开始] of the story.