D) Water purification programs because if water is contaminated, it can produce a huge amount of illness and sickness worldwide.
Correct answer choice is:
D. Frequency.
Explanation:
AC frequency is the number of periods per moment in an alternating current (ac) sine wave. Said different mode, the frequency is the scale at which the current varies course per instant. It is estimated in hertz (Hz), a global unit of measure wherever 1 hertz is equivalent to 1 cycle per instant.
To keep his chin up and to continue to work on his grades in order to bring happiness to the house. Seeking a relative or close friend for support would also be the best option in pushing through these tough times.
