Which option correctly identifies the parts labeled $a$ and $b$ in the given figure?

In the given figure,what do the labeled parts '$a$' and '$b$' represent respectively?

What is the structure labeled as $A$ in the given figure made of?

Which of the following statements are incorrect?
$(i)$ Plant cells have centrioles which are absent in almost all animal cells.
$(ii)$ Ribosomes are the site of protein synthesis.
$(iii)$ The middle lamella is a layer mainly of calcium carbonate which holds the different neighbouring cells together.
$(iv)$ In animal cells, steroidal hormones are synthesized by smooth endoplasmic reticulum.
Of the above statements:

$A$ chemical substance that,when irradiated with $UV$ rays,absorbs radiation and emits visible light is called:

Select the correct match for $X$ and $Y$:

Column $X$	Column $Y$
$(1)$ Typical animal cell	$(P)$ Multinucleate
$(2)$ Zygote	$(Q)$ Uninucleate
$(3)$ Human $RBC$	$(R)$ Binucleate
$(4)$ Plant embryo sac	$(S)$ Enucleate