Answer:
The correct option is B) after sentence 2
Step-by-step explanation:
The sentence which the author wants to add in section 5 is a kind of conclusion of the statements 1 and 2. Hence, the best option to place the sentence is at the end of the section 5.
Other options, like option A, cannot be considered because the sentence which the author wants to add is a conclusive sentence and it will make no sense if placed n between sentence 1 and sentence 2.