If the engine is naturally aspirated, or i
题型：单项选择题
问题：
If the engine is naturally aspirated, or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap（）,ie when both valves are（）, will be and the exhaust valve will close some 10°top dead canter（）.
A.open；short；after
B.closed；short；after
C.open；long；before
D.closed；long；before