The double layered sac surrounding the heart is the pericardium
The answer to this question would be: absorbing water.
A lower water potential solution will induce osmosis to plant cells. In this case, the water will move to the plant cells since solution water potential nearby cells are lower. The plant will continue to accept water until the cells bloated, causing the pressure inside cells increases until the water pressure will gradually stop the osmosis. The plant cell rarely burst as it has cellulose wall, unlike animal cells.
At least 75% of the history of the earth
The answer is (C) Core, Radiative Zone and then the Convection Zone
