This is a cell, which is the basic unit of all life. all organs in human bodies are made of cells and require oxygen to survive. which two systems work together to deliver oxygen to cells throughout the body?
a) skeletal and endocrine
b) digestive and endocrine
c) skeletal and respiratory
d) respiratory and cardiovascular

A20 cm long spring is attached to a wall. the spring stretches to a length of 22 cm when you pull on it with a force of 100 n. what is the spring constant

Which basic property determines a colored light's placement on the spectrum of visible light? a. speed b. frequency c. amplitude d. velocity

In a game of pool, ball a is moving with a velocity v0 of magnitude v0 = 15 ft/s when it strikes balls b and c, which are at rest and aligned as shown. knowing that after the collision the three balls move in the directions indicated and assuming frictionless surfaces and perfectly elastic impact (that is, conservation of energy), determine the magnitudes of the velocities va, vb, and vc.