Which muscle shows striations?

Which contractile protein of skeletal muscle is associated with $ATPase$ activity?

Select the correct statements regarding the mechanism of muscle contraction.
$A.$ It is initiated by a signal sent by $\text{CNS}$ via a motor neuron,not a sensory neuron.
$B.$ Neurotransmitter generates an action potential in the sarcolemma.
$C.$ Increased $Ca^{++}$ level leads to the binding of calcium with troponin on actin filaments.
$D.$ Masking of the active site of actin prevents contraction; unmasking leads to contraction.
$E.$ Utilising the energy from $\text{ATP}$ hydrolysis to form a cross-bridge.

What is the full form of the following terms used in muscle structure?
$(1)$ $A$-disc
$(2)$ $I$-disc

Cardiac muscle fibers differ from skeletal muscle fibers in that they are -

Bone-dissolving cells are known as..........