Earth's crust is made of rock, and rock is made of natural substances called minerals. There are three main types of rock: sedimentary, igneous, and metamorphic rock. Each type is produced in different ways. The oldest rocks on Earth were formed about 3.8 billion years ago.
There are tons of answers you could have.
One, for example:
Increased levels of CO2 decreases DO levels in the water and suffocates organisms, leading to population drops that can cause a genetic bottle neck effect, thus decreasing overall biodiversity. This could lead to extinction
GTAATG
c = g
t = a
Just switch the letter around to find the opposite of your given strand.