1) The charge left on the fur is equal and opposite to the charge transferred to the rod:

In fact, when the rod is rubbed with the fur, a net charge of

has been transferred to the rod, leaving it negatively charged. If we assume the fur was initially neutral, this means that we have now an excess of positive charges on the fur, and the amount of this charge must be equal (in magnitude, but with opposite sign) to the charge transferred to the rod.
2) The mass transferred to the rod is equal to the total mass of the electrons transferred to the rod.
The charge transferred to the rod is

The charge of 1 electron is

So the number of electrons transferred is

The mass of 1 electron is

, therefore the total mass transferred to the rod is
We are given the following conditions:

Since we are told it slows down at a constant rate, we know we are dealing with uniformed accelerated motion, or UAM for short.
So we look at our kinematics equation that contains the given variables.

This contains our target variable and our initial conditions. Plug and chug, we get:

Thus the answer is:
a = -7m/s^2
Hope this helps!
<h2>Hey there! </h2>
<h3>The correct option is:</h3>
<h2>'B' material </h2>
<h2>Hope it help you </h2>
B. the skin produces sweat