We were told not to touch the equipment in the laboratory unless ________.
| A．allowed to do | B．allowing to do |
| C．allowed to | D．allowing to |
He was reading his book, completely _______ to the world.
| A．lost | B．losing |
| C．to lose | D．to have lost |
She looks forward every spring to _______ the flower-lined garden.
| A．visit | B．paying a visit |
| C．walk in | D．walking in |
Anyone _______ bags, boxes, or whatever, was stopped by the police.
| A．seen carry | B．seen carrying |
| C．saw to carry | D．saw carrying |
I would love _______ to the party last night but I had to work extra hours to finish a report.
| A．to go | B．to have gone |
| C．going | D．having gone |
Every evening after dinner, if not ________ from work, I will spend some time walking my dog.
| A．being tired | B．tiring |
| C．tired | D．to be tired |