it's the safer than --------by plane.A.go B.going C.to go D.to going

it's the safer than --------by plane.A.go B.going C.to go D.to going
it's the safer than --------by plane.A.go B.going C.to go D.to going

it's the safer than --------by plane.A.go B.going C.to go D.to going
B than介词 后加ving

by by by by 全都填by 都填by 搭乘 ；by 交通工具基本的简单It

选B， than+doing