The function of a safety valve is

to blow off steam when the pressure of steam inside the boiler exceeds the working pressure
to indicate the water level inside the boiler to an observer
to measure pressure of steam inside the steam boiler
none of the above
✅ The correct answer is option A.

In order to give the primary balance of the reciprocating parts of a multi-cylinder in-line engines,

the algebraic sum of the primary forces must be equal to zero
the algebraic sum of the couples about any point in the plane of the primary forces must be equal to zero
both (a) and (b)
none of these
✅ The correct answer is option C.