No, it is false that you can see, smell, and taste microorganisms (in general). Of course you can see them if you use a microscope, but not with your bare eyes. And if you were to assemble enough of them there is of course the possibility you could taste them, but not when they're on their own.
I think its b) the mech. replaced the air filter
Answer:
im pretty sure its formative.
Explanation:
I would need to see the statments to be sure but i belive that the answer is,
eouropeans would travel to america on ships infested with rats carrieing these deadly diseases which is also to be belived that is why america has these diseases in the first place.