Answer:
d. Relative humidity increases.
Explanation:
The expression of relative humidity in terms of absolute humidity, absolute pressure and saturation pression at measured temperature is:

When temperature decreases, the saturation pressure decreases also and, consequently, relative humidity increases. Therefore, the right answer is option D.
Answer:
A. 1.6 N/cm
Explanation:
spring constant = 21/13 = 1.6 N/cm
To solve the problem, it is necessary the concepts related to the definition of area in a sphere, and the proportionality of the counts per second between the two distances.
The area with a certain radius and the number of counts per second is proportional to another with a greater or lesser radius, in other words,


M,m = Counts per second
Our radios are given by



Therefore replacing we have that,






Therefore the number of counts expect at a distance of 20 cm is 19.66cps
Gravitational potential energy -> Kinetic energy -> Mechanical energy -> Electrical energy.
The water starts up (potential) and flows down (kinetic), the flowing water turns a big wheel (mechanical) which creates electricity (electrical).