1) Which of the following activities would employ isometric contractions? a) Flexing the elbow
b) Chewing food
c) Maintaining an upright posture
d) Running
e) Writing

c. Maintaining an upright posture

Explanation:

"Isometric contraction" is all about increasing the tension in the muscles without shortening or lengthening the length of the muscles. There's also no movement.

Among the choices above, it is only "Maintaining an upright posture" that doesn't have movement; therefore, this employs the isometric contraction. This kind of contraction increases a person's strength. Another example of this contraction is holding a weight overhead.

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

b. the carbon cycle ensures living things have a source of hydrogen