1 . ________ snow is widely used to replace natural snow at the ski resorts so that visitors can access winter sports, round the year.

A．Substantial

B．Virtual

C．Artificial

D．Multiple

2 . Innovation is key to business survival, and companies put ________ resources into encouraging employees to develop new ideas.

A．definite

B．primitive

C．substantial

D．reasonable

3 . Mary was greatly inspired though she made ________improvements in her English writing.

A．brilliant

B．modest

C．substantial

D．considerable

4 . The threat of malaria around the world saw a ________ reduction.

A．substantial

B．surrounding

C．sincere

D．swollen