单项选择题
A.must be provided
B.may be provided
C.have provided
D.can be provided
单项选择题 In order to ensure perfect atomization, the fuel oil （） before injection.
单项选择题 In large marine diesel engines cylinder oils usually contain additives formulated to impart the （） to clean the rings and grooves.
单项选择题 In general, （） is suitable for delivering small quantities at high pressure.