现在进行时的句式转换 — 英语选择题

Tom 正在给远方的笔友介绍家人此刻的活动。下列四个句子中，属于"现在进行时的一般疑问句并作肯定回答"且形式完全正确的一项是（　　） A. Does his sister doing her homework now? Yes, she does. B. Is his sister doing her homework now? Yes, she is. C. Is his sister doing her homework now? Yes, she is doing. D. His sister is doing her homework now? Yes, she is.