Theengineersinthislabspentseveralweeks_______theirplansforthenewbicycle.
A、countingHeworksinouruniversityasavisiting_______,notasaformalfacultymember.
Some lazy men would rather _______ than work.
This river forms a natural _______ between China and Korea.
Itisnot---_______formetoreturnallthebookstothelibrarynowbecauseIstillneedsomeofthemformyresearch.
When making modern cameras , people began to_______ plastics for metal.
