What made niches available for the radiation of mammals?

Many million years ago, dinosaurs and other giant animals have lived so almost all niches were taken by them. At that time, there were no many mammals and they were rather smaller groups. But, after dinosaurs extinction, some niches opened. Now, mammals could move to that niches and use all the resources now they are not used by other superior animals, so adaptive radiation of mammals could occur.

If these are the missing choices: a. to determine skin temperature, place the back of your hand against the patient's skin.b. determine body temperature by touching the patient's hands and feet.c. skin temperature will tell you very little about this patient's condition or well-being.d. the patient's skin temperature and color will likely be warm and red.my answer is: a. to determine skin temperature, place the back of your hand against the patient's skin. using the back of the hand to check for temperature rather than the palm is more effective because the back of the hand has more nerves that can feel and transmit the temperature than the palm.

Your gonna need to upload an image with the question : )