People can _______ running everywhere. Do you know what ______?
A. be seen; happened   
B. be seen; is happening 
C. see; happens

 People can  ______ running everywhere. Do you know what ______?

A. see, is happened        B. see, is happening

C. be seen, is happened     D. be seen, is happening

People can ________ running everywhere. Do you know what ________ ?

A. see; has happened

B. see; happens

C. be seen; is happened

D. be seen; is happening