Options:
a) When the sun is out, days in the desert can be very hot and, I think, many animals sleep in burrows or under rocks to stay out of the heat.
b) When the sun is out, days in the desert can be very hot, and, I think, many animals sleep in burrows or under rocks to stay out of the heat.
c) When the sun is out days in the desert can be very hot, and, I think, many animals sleep in burrows or under rocks to stay out of the heat.
d) When the sun is out, days in the desert can be very hot, and I think many animals sleep in burrows or under rocks to stay out of the heat.
Answer: d)When the sun is out, days in the desert can be very hot, and I think many animals sleep in burrows or under rocks to stay out of the heat.
Explanation:
The comma is referring to a punctuation mark that is used in every language. A look of a comma is considering shape of an apostrophe and it has big importance in the sentence because it has ability to make the sentence more understandable and meaningful.
In this case, commas are there to prevent misreading, conclusion and misunderstanding of the sentence. It is also used to separate conjunction ''and'' and independent clause.
