[Sabio]

To which of the following labeled area does Calcium entry promote the release of intracellular Calcium?

 

[indian]

I choose A

 

[khanar]

I choose B, which is the junction of A and I bands which is the site of T tubules which are the site of Calcium entry.

 

[ahassan]

I also pick B

 

[Sabio]

The correct answer

The correct option is A
T tubules are inserted at Z lines in cardiac muscles and at junction of the A and I band in skeletal muscles.
Since the question is talking about a Calcium dependent Calcium release then it must be the cardiac myocyte.
A is pointing to Z line.