Which is the best way to combine these two sentences?

Question

Breathing all that dust was not good for people's health. Many people got sick.

a. Breathing all that dust was not good for people's health, and many got sick

or
b. Breathing all that dust was not good for people's health, because many people got sick.

Answer 1

B is the best choice.

Answer 2

Sorry, but B is not the best choice. Getting sick was not the cause of "breathing all that dust..."

So either use A or turn B around:

Many people got sick because breathing all that dust was not good for people's health.