Nucleophilic addition reactions involve the addition of a nucleophile to an electrophilic center, resulting in the formation of a new bond. These reactions are commonly observed in organic chemistry and play a crucial role in various chemical transformations.

In nucleophilic addition reactions, there are several factors that can be observed, including changes in bond angles, repulsion between electron pairs, and changes in free energy. Let's discuss each option and explain why option 'B' is not observed in nucleophilic addition reactions.

Bond angle decreases and repulsion increases:
- When a nucleophile attacks an electrophilic center, it often leads to the formation of a new bond, which can result in a decrease in bond angle.
- As the nucleophile approaches the electrophilic center, the electron pairs start to repel each other, leading to an increase in repulsion.

Bond angle and repulsion both decrease:
- This option is incorrect because in nucleophilic addition reactions, the bond angle may decrease due to the formation of a new bond, but repulsion between electron pairs generally increases as the nucleophile approaches the electrophilic center.

Repulsion and free energy both increase:
- This option is also incorrect because repulsion between electron pairs generally increases as the nucleophile approaches the electrophilic center, but the change in free energy depends on the specific reaction and cannot be generalized.

Repulsion increases and free energy decreases:
- This option is incorrect because repulsion between electron pairs generally increases as the nucleophile approaches the electrophilic center, but the change in free energy depends on the specific reaction and cannot be generalized.

In summary, the correct answer is option 'B' because both the bond angle and repulsion do not decrease in nucleophilic addition reactions. The other options are either partially correct or cannot be generalized for all nucleophilic addition reactions.

Correct anwser is B