18. Circle the letters of the sentences that are true about aquifers. a. They are permeable rock layers that are saturated with water.
b. They are recharged or refilled as rainwater seeps into them.
c. They are often made of shale and unbroken granite.
d. Many people rely on aquifers for drinking water.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

the answer is c.) there is a warm front in region a and a stationary front in region b.

they both go up but then go back down. they both end lower than they started. lastly, they both are competitive/the second on.

explanation:

it’s lava came from an explosive eruption