The sentence to be added in the essay should be added, after sentence 5 as part of the claim.
What is claim?
Claim is a formal request for saying something.
Because, the sentence claims that the researchers are working on the batteries that stores energy that is generated from the solar power, so that it could be used at all times. and the lines 5 just added that how pursuing alternative fuel source would be the key solution for energy crisis.
Hence the correct option is, after sentence 5 as part of the claim.
To know more about claim:
https://brainly.com/question/12861905
#SPJ2