The opening and closing of this structure on a plant leaf allows for water and gas exchange to occur. a) xylem b) phloem c) stomata d) guard cells

C) stomata

Each stoma is surrounded by two guard cells, which can open/close depending on environment. When there is moisture, the guard cells swell with water, and force the stoma to open and allow gas exchange to occur.

sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times