The word marked in bold in the sentence above is the word that has an error. The correct thing would be to write the word "gases" without using the apostrophe (') after the last "S", since the apostrophe is used to cause the impression of possession and it has already been used, correctly in the word "Star's".
Out of all of them it makes the most sense, because he isn't showing pride. The grandpa isn't being rude about the situation but it also isn't showing a "bond" between them.
