The correct answer is option B, that is, it ended during the Mesozoic era.
The Cretaceous refers to a geological period, which persisted for 79 million years. It spans from the termination of the Jurassic period, that is, 145 million years ago, to the commencement of the Paleogene period, that is, 66 million years ago. It is the last period of the Mesozoic Era.
The period exhibited comparatively warm climate, leading to the formation of high sea levels, which formed various shallow inland seas. These waters got populated with marine reptiles, while dinosaurs persisted on land.