Which changing external condition triggers the salivary glands?
a. lack of oxygen
b. lack of water
c. disease-causing agents
d. change in temperature

The correct answer is B. Lack of water. When there's no water and you start to dehydrate, your salivary glands start working extra hard because your mouth can't be dry and the salivary glands produce saliva to keep the mouth and the throat dry. If your throat and mouth are dry you can't even swallow.

Because the earth is not round ,but it may seem round when viewed from ,our planet but true some points earth is not round was an oblate spheroid -a square that it squashed as globe however is not even a perfect oblate spheroid.in fact isaac newton's first proposed that earth was not perfectly round but it was an oblate spheroid instead.that mean a square that is squashed as its poles and swollen at the