21.is the loss of electrons from one substance, while is the addition of electrons to the other substance?

A. Reduction / Oxidation

B. Reduction / Digestion

C. Digestion / Breakdown

D. Oxidation / Reduction

thinking it would be d not too sure but i think it's right

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint

. the sierra madre fault zone of southern california

. the san andreas fault california

the circled areas are referred to   as sunspots.   the sunspots are cooler than the   surrounding area.

sunspots are temporary phenomena on the photosphere of the sun that appear visibly as dark spots compared to surrounding regions. they correspond to concentrations of magnetic field flux that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere.