What technological advancement was necessary before scientists could begin to observe cells? a. invention of the microscope b. invention of the balance c. invention of the telescope d. invention of the thermometer

A : microscope will be your answer

the correct answer would be

A) invention of the microscope

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands