Why is it important to know a person's rhesus factor before a blood transfusion? A patient who is Rh can receive only Rh– blood. A patient who is Rh– can receive only Rh blood. A patient who is Rh can receive only Rh blood. A patient who is Rh– can receive only Rh– blood.

In the image, layer a is the topmost layer. layer c contains fossils from the precambrian era. layer b contains dinosaur fossils, and layer a contains fossils of mammals. which two statements are supported by this evidence? 1. mammals lived before the precambrian era. 2. dinosaurs and mammals existed in the precambrian era. 3. dinosaurs evolved after precambrian organisms. 4. precambrian organisms evolved after dinosaurs. 5. precambrian organisms were the first life-forms to become fossilized, according to this sample.