Because

She's not going to the party because she's feeling sick.

The sunburn because he to stay outside for too long.

Her absence because the meeting to be postponed.

The garden is flourishing because it gets plenty of sunlight.

He didn't want to dance because he didn't know how. "Because he didn't know how?!"

She didn't want to ride the roller coaster because it was too scary. "Because it was too scary?!"

She is happy because she is going on vacation next week.

He missed his bus because he overslept this morning.

She couldn't sleep because she was too excited for her birthday.

He's studying hard because he wants to get good grades.

She bought a new dress because she has a date tonight.

He doesn't like seafood because he is allergic to it.

He was late for work because his car broke down.

We canceled our plans because of the rainy weather.

Her because explanation of the issue helped to clear up the confusion.