Which of the following is the best an example of an informal word that means “difficult”?

a. arduous
b. onerous
c. struggle
d. tough

for example: in, he, a,from

the answer is not

first person

explanation:

the apollo program, also known as project apollo, was the third united states human spaceflight program carried out by the national aeronautics and space administration (nasa), which succeeded in landing the first humans on the moon from 1969 to 1972.