D) explain why a high frequency carrier signal is needed in a communication system.

High frequency carrier signal has high power than low, so the information can be transmitted to a longer distance without distortion.

Explanation:

Instantaneous amplitude of the carrier signal is varied in proportion to the message signal. Since, frequency of the carrier signal is very high, the energy of the message signal improves and the information can be transmitted to a longer distance without distortion

emily ruth's annual premium is $1058.50

step-by-step explanation:

emily ruth is a female of 27 years age purchasing 20 year endowment insurance with face value $25000.

from the given table,

for females, the age of a male 3 years younger should be used.

so, we have to check for 24 year male for 20 year endowment.

it is 42.34 for every $1000 face value.

for a face value of $25000,

it is 25 * 42.34 = $1058.50

∴ emily ruth's annual premium is $1058.50

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it