cytosine

"It fits the purpose."

"Hydrogen is the simplest chemical element, with only one proton in its atom. "

"The sequence of events in the school play was: introduction, conflict, climax, and resolution. "

"Where he went after he left the house is a puzzle."

"The scientist studied the guanine content in the DNA samples from the ancient fossils. "

"The pharmaceutical company is researching a new drug that contains a specific heterocycle known for its potential anti-inflammatory properties. "

"Airplanes did not always exist as a form of transportation."

"By now, you must surely know which is which."

"The teacher's lesson plan was together, covering all the key concepts logically. "

"I’d like another piece of pie."

"Here are the pairs of socks I washed. "

"The student means their lost homework, feeling very sad about the missing paper. "