What is the function of the iris in the eye of a frog?

Endoplasmic reticulum or sarcoplasmic reticulum plays a major role during

Match the following columns and select the correct option.

Column-$I$	Column-$II$
$(a)$ Floating Ribs	$(i)$ Located between second and seventh ribs
$(b)$ Acromion	$(ii)$ Head of the Humerus
$(c)$ Scapula	$(iii)$ Clavicle
$(d)$ Glenoid cavity	$(iv)$ Do not connect with the sternum

$(a) \quad (b) \quad (c) \quad (d)$

Study the following sentences:
$I.$ The accumulation of pyruvic acid in the muscle causes fatigue.
$II.$ $ATP$ is resynthesized in the muscle by the phosphorylation of $ADP$ by a phosphogen.
$III.$ Cori cycle involves muscles and liver.
$IV.$ The phosphogen in the vertebrate muscle is arginine phosphate.
The correct set of statements regarding muscle contraction is:

In children,the bones are more flexible and less brittle because their bones have:

Which of the following is $NOT$ a function of the skeletal system?