She stayed at home during the whole summer vacation（）she could look after her old grandmother.

单项选择题So little（）about China that he could not find Beijing in the world map.

A．the foreigner knew
B．did the foreigner know
C．the foreigner has known
D．has the foreigner known

单项选择题The DNA test, together with other tests,（）the prisoner's innocence.

A．proves
B．prove
C．proving
D．have proved