Professor Brand,who enjoys welcoming international students

Professor Brand,who enjoys welcoming international students to her home on Thanksgiving-----
A served the traditional turkey,dressing in Pilgrim clothing
B dressed in Pilgrim clothing to serve the traditional turkey.
答案为什么是B而不是A?
The underside of the starfish is covered with hundreds of tube feet,which it uses ( )on to prey.
A to walk around,for attaching tightly to rocks,and holding
B.for walking around ,attaching tightly to rocks,and holding
为什么不是A,