When the sea floor spreads or collides it creates breakages which would be ocean ridges and deep sea trenches
Lean women with a BMI less than 20 have an increased risks of preterm delivery, and deliver- ing a low-birth weight infant. The correct option among all the options that are given in the question is the first option or option "a". Similarly it is not good to gain excess weight while in the pregnancy stage, as the baby might grow at a larger proportion that required.
Geology is a branch of natural science that studies rocks, how they form, etc.
This field of study enabled us to know the age of Earth, the different layers that make up earth amongst many other things.
Hope it helped,
BioTeacher101
(If you have any questions, feel free to ask them in the comments)