It was not until ________ that ________ to prepare his lessons．

A．did his father come in; the boy began

B．his father came in; the boy began

C．did his father come in; did the boy begin

D．his father came in; did the boy begin

It was not until ________ that ________ to prepare his lessons．

A．did his father came in; the boy began

B．his father came in; the boy began

C．did his father come in; did the boy begin

D．his father came in; did the boy began

It was not until ________ that ________ to prepare his lessons．

A．did his father come in; the boy began

B．his father came in; the boy began

C．did his father come in; did the boy began

D．his father came in; did the boy begin