R = ρ L/A. R= resistance, ρ= resistivity, L= length of the conductor. A = area of the conductor. Resistance is directly proportional to the length of the conductor. So if length of the conductor is decreased, resistance will also decrease. Hence A is the correct option
It increases across a period but it decreases down a group.
<u>Answer</u>:
The stream flowing at a speed of 
<u>Explanation</u>:
Given:
Distance = 2km (both in upstream and downstream)
The speed in still water be x km/hr.
The speed in upstream = 4-x
Speed in downstream = 4+x
Solution:
We know that, Speed = distance/time
So, Time = distance/speed
Therefore,




By cancelling 2 on both sides,




Result:
Thus the speed of the stream is 
Kinetic energy E = m * v^2
<span>Since the acceleration of both books will be -neglecting air resistance - the same, the kinetic energy will be directly proportional to the mass of the book.</span>