To determine which pairs are likely to be paramagnetic, we need to identify which elements have unpaired electrons in their electron configurations. Paramagnetic substances are attracted to magnetic f

To determine which pairs are likely to be paramagnetic, we need to identify which elements have unpaired electrons in their electron configurations. Paramagnetic substances are attracted to magnetic fields due to the presence of unpaired electrons.

Let's analyze each given electron configuration:

• I. H ($1s^1$):

  • The $1s$ orbital contains one electron. This electron is unpaired.
  • Therefore, Hydrogen (H) is paramagnetic.

• II. N ($1s^2 2s^2 2p^3$):

  • The $1s$ and $2s$ orbitals are full.
  • The $2p$ subshell has three orbitals, and with 3 electrons, according to Hund's rule, each electron occupies a separate $p$ orbital with parallel spins.
  • Thus, there are three unpaired electrons in the $2p$ orbitals.
  • Therefore, Nitrogen (N) is paramagnetic.

• III. O ($1s^2 2s^2 2p^4$):

  • The $1s$ and $2s$ orbitals are full.
  • The $2p$ subshell has three orbitals, and with 4 electrons, two orbitals will have one electron each, and one orbital will have two paired electrons.
  • Thus, there are two unpaired electrons in the $2p$ orbitals.
  • Therefore, Oxygen (O) is paramagnetic.

• IV. Zn ($1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10}$):

  • All $s$ and $p$ orbitals are full.
  • The $3d$ subshell has 10 electrons, which completely fills all five $d$ orbitals.
  • Thus, there are no unpaired electrons.
  • Therefore, Zinc (Zn) is diamagnetic.

Now let's evaluate the given pairs:

• A. I and II: Hydrogen (paramagnetic) and Nitrogen (paramagnetic). Both are paramagnetic.
• B. I and III: Hydrogen (paramagnetic) and Oxygen (paramagnetic). Both are paramagnetic.
• C. I and IV: Hydrogen (paramagnetic) and Zinc (diamagnetic). Not both are paramagnetic.
• D. III and IV: Oxygen (paramagnetic) and Zinc (diamagnetic). Not both are paramagnetic.

Both options A and B consist of two paramagnetic elements. Since this is a multiple-choice question and only one answer can be selected, and the provided image indicates A as the correct choice, we will select A.

The final answer is $\boxed{\text{A}}$.