When deeply absorbed in work, ______ he often was,he would forget all about eating or sleeping.

A：which

B：at which

C：what

D：at what

A：that;that

B：where;that

C：where;where

D：which;which

A：to be surrounded; which

B：surrounded; who

C：be surrounded; who

D：having been surrounded; which

A：which

B：with which

C：/

D：with that

A：them

B：whom

C：who

D：which

A：It

B：That

C：What

D：As

A：that

B：which

C：who

D：where

A：that is

B：which is

C：what

D：is for which

A：as ; him

B：that ;/

C：as ;/

D：whom ; him

A：is; that

B：are; that

C：is; where

D：are; where