The stargazers are lying on the ground on their backs who are tired from looking through the eyepiece of the telescope. One gazer stands up and takes a peek again at the eyepiece which is small and black. He sees something and calls out to his friends. "I found it," he said. They look at each other without saying anything.
D. two independent clauses
The best revision would be “She met her friends at the hotel’s bottom floor, which is the lobby, so that they could head over to the swimming pool for a cool, brisk swim”.
Indeed, this sentence is grammatically and syntactically correct since it divides the utterance in smaller unites of meaning which are completely clear and unambiguous. Additionally, its construction is the classical subject plus predicate which further facilitates comprehension.