The la brea tar pits are an example of a fossil fuel that
a. is a quickly renewable resource.
b. takes centuries to create.
c. is made of decomposed human bones.
d. will never become scarce.

True or false: (a) the strings of little red dots represent carbohydrates. (b) the model is called a bilayer because there are two main types of molecules present, lipids and proteins. (c) the many black lines represent amino acid tails. (d) this model shows membrane transport. (e) the blue ovals are hydrophobic. (f) the blue ovals represent phospholipid heads.