Which factor made the diseases transmitted by europeans so deadly for the native american populations of north america?

a. the native people had different habits.
b. the native people lacked natural immunities.
c. the native people were physically weaker then europeans.
d. the native people wore less clothing.

Hi!

The correct answer is going to be that The Native People lacked natural immunities. 

Since they had never been exposed to Europeans before, they did not have any defences developed from the diseases they faced.

It's because of this that diseases such as Smallpox were so devastating to the Native American population.

Hopefully, this helps! =)