You are correct, the answer is C.
Good insulators are materials that do not allow heat, electricity, light or sound pass through easily. Materials like steel and silver (which are metals) are not good insulators because they make good conductors. They easily allow heat, electricity and the like pass through them.
Thus, the answer is letter C. Rubber.
68 degrees would be the answer
Answer:
(a) 3107.98 J
(b) 14530.6 J
Explanation:
mass, m = 3.56 kg
angular speed, ω = 179 rad/s
Moment of inertia of solid cylinder, I = 1/2 mr^2
where, m is the mass and r be the radius of the cylinder.
(a) radius, r = 0.330 m
I = 0.5 x 3.56 x 0.330 x 0.330 = 0.194 kgm^2
The formula for the rotational kinetic energy is given by

K = 0.5 x 0.194 x 179 x 179 = 3107.98 J
(b) radius, r = 0.714 m
I = 0.5 x 3.56 x 0.714 x 0.714 = 0.907 kgm^2
The formula for the rotational kinetic energy is given by

K = 0.5 x 0.907 x 179 x 179 = 14530.6 J

The best method to use in prevention of self-demagnetization of a permanent magnet is by use of a keeper. Keepers were also commonly known as amateurs. They help in storing magnets safely, especially those that have low coercivity ( magnets that are extremely susceptible to stray fields).

Hope It Helps!
<span>The Compound Eye. The arthropod (e.g., insects, crustaceans) eye is built quite differently from the vertebrate eye (and the mollusk eye). Arthropod eyes are called compound eyes because they are made up of repeating units, the ommatidia, each of which functions as a separate visual receptor.</span>