Dalton proposed the first atomic model. he's thinking that

a. atoms are all alike.

b. atoms are solid balls.

c. smaller particles are found inside atoms.

d. atoms can be divided into smaller parts.

Abird flies by moving its wings up and down. which two systems are most directly responsible for the movement of a bird's wings? a. skeletal and muscular systems b. respiratory and muscular systems c. skeletal and digestive systems d. respiratory and digestive systems