Normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. However, when rain combines with sulfur dioxide or nitrogen oxides—produced from power plants and automobiles—the rain becomes much more acidic. Typical acid rain has a pH value of 4.0.
Effacement: The cervix – which is normally long and thick, measuring about 1-2 inches, starts to get shorter and thinner. This process is known as effacement. As the cervix gets more and more effaced, it gets shorter and shorter and “pulled up” into the lower part of the uterus.
Dilation: At the same time, the cervix softens and begins to open up – known as dilation. This widening, allows a smooth passage for the baby’s head and the rest of the body from the uterus into the vaginal canal.
Answer:
December - February is summer in Argentina.
Explanation:
Answer:

Explanation:
To differentiate: 
Solution:
Use product rule:
and the following formulae:

![(10\,sinx\,\,cos x)'=10[(sinx)'cosx+(sinx)(cosx)']\\\\=10[cosx\,cosx-sinx\,sinx]\\\\=10[cos^2x-sin^2x]](https://tex.z-dn.net/?f=%2810%5C%2Csinx%5C%2C%5C%2Ccos%20x%29%27%3D10%5B%28sinx%29%27cosx%2B%28sinx%29%28cosx%29%27%5D%5C%5C%5C%5C%3D10%5Bcosx%5C%2Ccosx-sinx%5C%2Csinx%5D%5C%5C%5C%5C%3D10%5Bcos%5E2x-sin%5E2x%5D)
Use 

the frog is now a predator