___ there are living creatures in the outer space as those on Earth hasn’t been proved until now.
| A．How | B．When | C．Where | D．Whether |
．There are five pairs______, but I’m at a loss which to buy．
A．to be chosen B to choose from C . to choose D for choosing
．Paul doesn't have to be made ______ .He always works hard．
| A．earn | B． to learn | C．earned | D．earning |
．We agreed ______here but so far she hasn't turned up yet．
| A．having met | B．meeting | C．to meet | D．to have met |
．The boy wanted to ride his bicycle in the street，
but his mother told him______．
| A．not to | B．not to do | C．not do it | D．do not to |
. She pretended ______ me when I passed by .
| A．not to see . | B．not seeing | C．to not see | D．having not seen. |