A car engine cannot run smoothly without motor oil. our body cannot function efficiently without vitamins.
Afortunately
BGradually
CSimilarly
DConfidently
网友回答
A. fortunately
B. Gradually
(答案→)C. Similarly
D. Confidently
解析：副词辨析。A幸运地是；B逐渐地；C相似地；Ｄ有信心地；结合句意可知Ｃ正确。句意：没有基友，汽车发动机就不能顺利运转。相似地是没有维他命，我们的身体也不能有效的运转。