Answer:
B
Explanation:
it dropped 12 ft in 3 seconds.
but the standard measurement is ft per second. not ft per 3 seconds.
what do we need to do ?
we need to transform the ft per 3 seconds number into a ft per second number.
mainly we use common sense.
if something moves 12 ft / 3 seconds, how far will it have moved already after 1 second (which is the standard unit of measurement) ?
a ratio, a rate - they are all expressed by fractions.
miles per hour, ft per second, ... these are all fractions, as they express a relationship between one dimension and the other.
so, when we have 12 ft / 3 seconds, we have the fraction 12/3 ft/sec = 4/1 ft/sec = 4 ft/sec
there you have it almost automatically.
this question here tries to be tricky.
it actually asks for the direction of the movement, and not just the speed.
for that we need to know that going down is considered negative change of height, while going up is considered positive change of height.
what do we need here ?
descent, going down.
so, we need a negative sign.
and therefore B -4 ft/sec is the right answer.