Answer: Sacroplasmic recticulum is an organelle in the muscle cells that stores calcium used in muscle contraction.
Explanation:
Muscle contraction is the activation of sites in the muscle fibres that produce tension. It does not necessary means muscle shortening as tension can be generated without any change in muscle length.
Sacroplasmic recticulum is similar to endoplasmic recticulum and its is an organelle in the muscle cells that stores calcium needed for muscle contraction. It contains the ion channels pump that are responsible for pumping calcium into the sacroplasmic recticulum.
The answer to this question would be hypertonic.
If the chloroplast is going to be pushed against the cell wall, probably the water around the cell wall is decreased, causing it to suck up the water inside. Then, the solution must be causing the cell to lose water. The cell will lose water if put in a hypertonic solution. In a hypertonic solution, the osmotic pressure of the solution is higher than the cell, make it attract water from cells.
Scientific theories are hypotheses that are supported by repeated experiments.