nonchalant

"Despite the loud argument next door, she remained unconcerned, focusing on her book. "

"The scientist carefully examined the strange matter in the lab. "

"The frenetic was clearly overwhelmed by the last-minute rush before the school play. "

"It was a surprise to see the captain, who had always seemed so serious, laugh so heartily."

"to detach the tag from a newly purchased garment"

"The indifferent student didn't care about the upcoming exam. "

"The United States is in an awkward situation with debt default looming."

"He casually mentioned that he had a new job. "

"The ballet dancer walked with a graceful attitude."

"The cashier carefully handled the delicate glass ornament. "

"After a long day at work, I relaxed by taking a hot bath. "

"You need to behave yourself, young lady."