选 B
where to study = where I should study
考查宾语从句
A where shall we study （×）应该用陈述句语序
C how we should do （×）缺少宾语,应该加个 it
D how to do （×）缺少宾语,应该加个 it何不选C？C 也是缺少宾语how to do itwhat to do