Read the following sentences.

The flash mob startled us. We were too enthralled to leave.

Which of the following correctly combines these two sentences into a compound sentence?
A.
Even though the flash mob startled us, we were too enthralled to leave.
B.
The flash mob startled us, but we were too enthralled to leave.
C.
The flash mob startled us, we were too enthralled to leave.
D.
Since the flash mob startled us, we were too enthralled to leave.

Please select the best answer from the choices provided

A
B
C
D