求解 以语法题

飘洋过海

The demand for airplane mechanics is expected to grow about ten percent a year in the next decade, largely because new federal rules calling for major modifications to older planes and because the air-lines are adding hundreds of new jets.

(A) new federal rules calling for major modifications to older planes
(B) new federal rules call for major modifications to older planes

向各位求解，为什么？thx

飘洋过海

悲剧了～ 脑子想的复杂了～

Jennifer789

选B吧 因为because后面加完整句子  A缺少谓语 加个are就行了