Dinosaurs which lived 150–200 million years ago were:

The correct answer is Giant reptiles. Dinosaurs were a diverse group of reptiles that dominated terrestrial ecosystems during the Mesozoic Era, which spanned from approximately 252 to 66 million years ago. The period 150–200 million years ago falls within the Jurassic period, a time when many iconic, large dinosaur species flourished. Dinosaurs exhibited classic reptilian characteristics, including scales, egg-laying, and a generally sprawling posture, although many were bipedal. Their immense size and variety solidified their status as the dominant terrestrial vertebrates of their time.

• Huge Mammals evolved much later, after the extinction of the dinosaurs. Mammals during the Mesozoic were generally small and nocturnal.
• Primitive birds evolved from small feathered dinosaurs, but dinosaurs themselves were not birds.
• Primitive amphibians were prominent much earlier in Earth's history (Paleozoic Era) and were generally smaller and less dominant than dinosaurs during the Mesozoic.