单项选择题

In a trunk type diesel engine piston, the thickness of the head or crown is determined by the()
Ⅰ.statically balanced
Ⅱ.heat dissipation requirement

A.Ⅰ only
B.Ⅱ only
C.both Ⅰ and Ⅱ
D.neither Ⅰ nor Ⅱ