The option(s) in which at least three molecules follow Octet Rule is(are)

The correct options are:
1. CO₂, C₂H₄, NO and HCl
2. CO₂, BCl₃, O₃ and C₂H₄

To determine which options have at least three molecules following the octet rule, let us analyze the Lewis structures and electron counts of each molecule mentioned in the options:

1. Carbon dioxide (${\mathrm{CO}}_2$):
The central carbon atom has 4 valence electrons and forms two double bonds (one with each oxygen atom).
Each oxygen atom has 6 valence electrons and shares 2 pairs with carbon, while retaining 2 lone pairs.
Carbon share: 4 shared pairs = 8 valence electrons.
Oxygen share: 2 shared pairs + 4 non-bonding electrons = 8 valence electrons.
Therefore, all atoms in ${\mathrm{CO}}_2$ obey the octet rule.

2. Ethene ($C_2{H}_4$):
Each carbon atom has 4 valence electrons. The two carbon atoms share a double bond (4 electrons) and each carbon shares single bonds with two hydrogen atoms (4 electrons).
Each carbon atom is surrounded by 8 valence electrons, thereby obeying the octet rule. (Hydrogen atoms follow the duplet rule, which is the stable configuration for the first shell).

3. Hydrogen chloride ($\mathrm{HCl}$):
The chlorine atom has 7 valence electrons and shares 1 pair with hydrogen, retaining 3 lone pairs.
Chlorine share: 1 shared pair + 6 non-bonding electrons = 8 valence electrons.
Thus, the chlorine atom obeys the octet rule.

4. Ozone ($O_3$):
Ozone consists of three oxygen atoms. The central oxygen forms a double bond with one terminal oxygen and a coordinate/single bond with the other terminal oxygen.
The central oxygen has 1 lone pair and 3 bonding pairs (6 shared electrons) = 8 valence electrons.
The double-bonded terminal oxygen has 2 lone pairs (4 electrons) and 2 bonding pairs (4 electrons) = 8 valence electrons.
The single-bonded terminal oxygen has 3 lone pairs (6 electrons) and 1 bonding pair (2 electrons) = 8 valence electrons.
Therefore, all oxygen atoms in $O_3$ obey the octet rule.

5. Nitric oxide ($\mathrm{NO}$):
Nitrogen has 5 valence electrons and oxygen has 6 valence electrons, giving a total of 11 valence electrons (an odd-electron molecule).
Because the total number of valence electrons is odd, at least one atom must have an incomplete octet.
In the Lewis structure of $\mathrm{NO}$, nitrogen has 7 valence electrons, so it does not follow the octet rule.

6. Boron trichloride (${\mathrm{BCl}}_3$):
Boron has 3 valence electrons and shares them to form three single covalent bonds with three chlorine atoms.
The central boron atom is surrounded by only 6 valence electrons (an electron-deficient molecule), so it does not obey the octet rule.

7. Nitrogen dioxide (${\mathrm{NO}}_2$):
Nitrogen has 5 valence electrons and each oxygen has 6, giving a total of 17 valence electrons.
Like $\mathrm{NO}$, ${\mathrm{NO}}_2$ is an odd-electron molecule where the central nitrogen atom has a single unpaired electron and does not satisfy the octet rule (it has 7 valence electrons in its outer shell).

8. Sulfuric acid ($H_2{\mathrm{SO}}_4$):
The central sulfur atom forms six covalent bonds (two single bonds to $-\mathrm{OH}$ groups and two double bonds to oxygen atoms).
The central sulfur atom has 12 valence electrons in its valence shell, which is an expanded octet. Therefore, it does not follow the octet rule.

Let us now check the number of molecules obeying the octet rule in the options:

• In the option CO₂, C₂H₄, NO and HCl:
- ${\mathrm{CO}}_2$: Obeys octet rule
- $C_2{H}_4$: Obeys octet rule
- $\mathrm{HCl}$: Obeys octet rule
Total = 3 molecules obey the octet rule (satisfies the condition "at least three").

• In the option CO₂, BCl₃, O₃ and C₂H₄:
- ${\mathrm{CO}}_2$: Obeys octet rule
- $O_3$: Obeys octet rule
- $C_2{H}_4$: Obeys octet rule
Total = 3 molecules obey the octet rule (satisfies the condition "at least three").