The number of orbitals present in the shell with $n = 4$ is

In a multi-electron atom,which of the following orbitals described by the three quantum numbers will have the same energy in the absence of magnetic and electric fields?
$1. n = 1, l = 0, m = 0$
$2. n = 2, l = 0, m = 0$
$3. n = 2, l = 1, m = 1$
$4. n = 3, l = 2, m = 0$
$5. n = 3, l = 2, m = 0$

Explain the energy order of orbitals in multielectron atoms.

Which one of the following statements is incorrect?

Arrange the energy of the $2s$ orbital in the following atoms in decreasing order: $H, Li, Na, K$.

In which of the following species,the ratio of $s$-electrons to $p$-electrons is the same?