A. It has mass.
Air is matter, and can't be seen thus not all matter can be seen.
Any liquid or gaseous is matter (water, air, etc.)
Since it can be liquid or gaseous it doesn't have to maintain it's shape and size to be matter.
You could be depressed from a lot of different things, from losing your job to someone passing away
Answer:c
Explanation: The plant is responding to external stimuli by growing toward light like our eyes adjusting to the light in the dark......................
