From what I can see it's D, I did this by simply examining the other answers and seeing that they are beneficial, so, from that information, this one must not be.
Answer:
50 N.
Explanation:
On top of a horizontal surface, the normal force acting on an object is equivalent to the force of gravity acting on the object. That is:

The mass of the block is 5 kg and the given force due to gravity is 10 N/kg. Substitute and evaluate:

In conclusion, the normal force acting on the block is 50 N.
Answer:
71.4583 Hz
67.9064 N
Explanation:
L = Length of tube = 1.2 m
l = Length of wire = 0.35 m
m = Mass of wire = 9.5 g
v = Speed of sound in air = 343 m/s
The fundamental frequency of the tube (closed at one end) is given by

The fundamental frequency of the wire and tube is equal so he fundamental frequency of the wire is 71.4583 Hz
The linear density of the wire is

The fundamental frequency of the wire is given by

The tension in the wire is 67.9064 N
C. Quarts watches is the correct answer