The reason that oscillating systems are good to use for clocks is:
A. The period of an oscillation does not depend upon amplitude.
B. Real mass-spring systems are frictionless and energy is perfectly conserved.
C. The frequency of an oscillator does not depend on mass.
D. The frequency of an oscillator does not depend on the strength of the spring.
E. Oscillators are efficient at turning motion into heat.

A. The period of an oscillation does not depend upon amplitude.

Explanation:

The period of a spring-mass system is:

T = 1/f = 2π√(m/k)

where f is the frequency, m is the mass, and k is the spring constant.

The answer isn't B.  There are no frictionless systems in the real world.

The answer isn't C or D.  As shown, the frequency is a function of both the mass and the spring constant.

The answer isn't E.  Turning motion into heat is not an advantage for a clock.

The correct answer is A.  The period of the system does not depend on the amplitude.

b.

explanation:

10.0

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards