Answer:
the external appearance of a plant community, which changes throughout the year in accordance with the succession of the phases of development of plants. As a rule, aspect is repeated year in and year out in almost identical sequence.
Answer:
B) Valves closing
Explanation:
A healthy heart makes a lub-dub sound with each beat. This sound comes from the valves shutting on the blood inside the heart. The first sound (the lub) happens when the mitral and tricuspid valves close.
