Question $3$ options:

a$)$

Deflation causes their dollar profit to be less than what they have invested. The selling price of their product will decrease because of deflation.

b$)$

Deflation means that they will have to recover and pay off their borrowed money for investment with the same amount of nominal dollars, but those dollars will be worth more.

c$)$

In deflationary times, business is slow. That is why there is deflation. Thus profits will be low.

d$)$

All of the above are correct.