Mrs. Smith shut the window lest ______ (外面的噪音会影响她儿子的睡眠).

A．She’ll definitely get a good grade because she didn’t use Internet sources.
B．She’ll probably do badly on her paper since she used nothing but Internet sources.
C．She’ll get a bad grade because she used Internet sources rather than anything else.
D．She wonders how well she’ll perform on her paper for using Internet sources.