I think the answer is A.
Ca sequestration means getting it back into the sarcoplasmic reticulum. The lower the frequency of stimulation, the more relaxation is possible and the more sequestration would take place during relaxation phases between the contractions. In E, the stimuli are very frequently applied, we havesustained contraction/tetanus, meaning that intracytoplasmic calcium will remain high to cater for the constant demand and not be sequestered back into the sarcoplasmic reticulum since there's no relaxation happening.
The answer to this is A. You can see the amount of calcium based on how low the stimulus frequency is. If you would check the given figure, the lowest point of stimulus frequency is A which means that this is the answer. Stimulus frequency refers to the amount or the rate that the stimulus is applied to the market.
Sequestration occurs when there is no blood in some spaces of the body wherein blood or other body fluids are expected. This can lead to various health complications and it should be addressed immediately. Sequestration may have a different meaning when used in chemistry.