The greenhouse effect
a.
is essential for life on earth
b.
warms earth’s atmosphere
c.
is a natural phenomenon
d.
all of the above

Once the plague became airborne, how could it then be spread?

Which one of these were common aspects of war efforts during world war 1 1. rationing 2. war bonds 3. using schools as military facilities 4. child soldiers 5. women working in factories circle all that apply

Who did the first work in creating vaccines