That's a velocity.
It has a speed and the direction of the speed.
A scientific theory is an explanation for the observed facts that can be tested and falsified. Therefore, its B.
Answer: a) 0.13*τ ; b) 2.08*τ
Explanation: In order to explain the discharg of a capacitor through a resistor, we have to consider the following:
Q(t)=Qo* exp(-t/τ) for a lose of 1/8-th of its charge
in this case, Q(t)=7/8*Qo=7/8*exp(-t/τ)
ln(7/8)*τ=-t
then, t= -ln(7/8)*τ =0.13
For a lose of 7/8 th of its charge , we have
Q(t)=1/7*Qo*exp(-t/τ)
t=-ln(1/8)*τ=2.08
