The correct answer is option 'D' - (I) effect.

The (I) effect, also known as the inductive effect, refers to the electron-withdrawing or electron-donating ability of a substituent group in a molecule. It occurs due to the polar nature of sigma bonds, where electrons are not equally shared between two atoms. Substituent groups can either withdraw or donate electrons through sigma bonds, affecting the electron density of the neighboring atoms or functional groups.

In this question, we are considering groups that have lesser electron-attracting power than hydrogen and are electron-repelling. Let's break down the answer in detail:

1. (E) effect:
The (E) effect, also known as the electromeric effect, refers to the donation or withdrawal of electrons by a substituent group through a pi bond or a multiple bond. It is not relevant to the given question because we are specifically asked about groups that have lesser electron-attracting power than hydrogen.

2. (-E) effect:
The (-E) effect refers to the withdrawal of electrons by an electron-withdrawing group through sigma bonds. It occurs when a substituent group has a higher electronegativity than the atom it is attached to. However, the question states that the groups are electron-repelling, which means they have lesser electron-attracting power than hydrogen. Therefore, the (-E) effect is not applicable here.

3. (-I) effect:
The (-I) effect, or the inductive effect, refers to the withdrawal of electrons by an electron-withdrawing group through sigma bonds. When a substituent group has a higher electronegativity than the atom it is attached to, it can withdraw electron density from the neighboring atoms or functional groups. This results in a decrease in electron density and a destabilizing effect on the molecule. Since the groups in question are electron-repelling and have lesser electron-attracting power than hydrogen, they exhibit the (-I) effect.

4. (I) effect:
The (I) effect, or the inductive effect, refers to the donation of electrons by an electron-donating group through sigma bonds. When a substituent group has a lower electronegativity than the atom it is attached to, it can donate electron density to the neighboring atoms or functional groups. This results in an increase in electron density and a stabilizing effect on the molecule. Since the groups in question are electron-repelling and have lesser electron-attracting power than hydrogen, they do not exhibit the (I) effect.

To summarize, the groups that are electron-repelling and have lesser electron-attracting power than hydrogen show the (-I) effect. This effect is characterized by the withdrawal of electrons through sigma bonds, resulting in a decrease in electron density and a destabilizing effect on the molecule.