Every 1/2 hour naomi stretches her neck every 1/3 hour she stretches her legs everyone 6 hours is stretches her on which part of her body will nyomi stretch 1 2/3 of an hour has passed

Arms and Legs

By inspection
From the diagram it is Legs and Arms

By calculation

It is a matter which of the three will accumulate to 23of an hour

,

Neck

Summing 12's only gives integer values giving 1,2,3,4... or
integer values + 12 and 0 +12 giving 12,112,212,...

So neck is excluded
'
Legs

Every 13:⇒13+12=23

Legs will be stretched at 23 hour
'
Arms

Every 16:=>16+16+16+16=46

Divide top and bottom by 2 giving:
4÷26÷2≡23

Arms will be stretched at 23 hour

a. is correct