How many subshells are associated with n=4?
A.4
B.3
C.2
D.1

Hint: A subshell is a group of orbitals. These are the collections of orbitals which share the same principal quantum number and angular momentum quantum number which is denoted by the letters s, p, d, f and so on. The electrons in an atom are arranged in shells that surround the nucleus.

Complete step by step answer:
The angular momentum quantum number l, can have any integer value from to.This quantum number describes the shape or type of the orbital. Orbitals with the same principal quantum number and the same l value belong to the same subshell. The value of n determines the possible values for l. For any given shell, the number of subshells can be found by l.
The fourth shell has 4 subshells, i.e. s, p, d, f.
The s subshell, which has 1 orbital with 2 electrons, the p subshell, which has 3 orbitals with 6 electrons, the d subshell, which has 5 orbitals with 10 electrons, and the f subshell, which has7 orbitals with 14 electrons.
 For total there are 16 orbitals and 32 electrons.
The s subshell is the lowest energy subshell and the f subshell is the highest energy subshell
And according to Pauli's Exclusion principle no two electrons can have the same set of quantum numbers, that is no two electrons can be in the same state.
This exclusion limits the number of electrons in atomic shells and subshells.

Hence, option A is correct.

Note:
The orbital names s, p, d and f stands for names given to groups of lines originally noted in the spectra of the alkali metals. These line groups are called sharp, principal, diffuse and fundamental. Each orbital can only hold 2 electrons max. There is a hierarchy, i.e. s orbitals will be filled before p orbitals which will be filled before d orbitals and so on.