Type of reactions shown by alkynes are `-`

Options

A. Electrophilic addition reactions
B. Nucleophilic addition reactions
C. Substitution reaction
D. All of the above

Explanation

To determine the types of reactions shown by alkynes, we can analyze the options provided and the characteristics of alkynes.

### Step-by-Step Solution:

1. **Understanding Alkynes**:
- Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond. The general formula for alkynes is CₙH₂ₙ₋₂.

2. **Identifying Reaction Types**:
- The question provides four options:
1. Electrophilic addition reaction
2. Nucleophilic addition reaction
3. Substitution reaction
4. All of the above

3. **Electrophilic Addition Reaction**:
- Alkynes can undergo electrophilic addition reactions. When an electrophile approaches the alkyne, it can add across the triple bond. For example, when hydrogen halides (like HBr) are added to alkynes, they can form haloalkenes.

4. **Nucleophilic Addition Reaction**:
- Alkynes can also undergo nucleophilic addition reactions. The triple bond can develop polarity, leading to a partial positive charge on one carbon and a partial negative charge on the other. Nucleophiles can attack the positively charged carbon, resulting in the addition of the nucleophile.

5. **Substitution Reaction**:
- Although substitution reactions are not common for alkynes, they can occur under specific conditions. For example, in the presence of ammonical silver nitrate or copper(I) chloride, alkynes can undergo substitution reactions where a hydrogen atom is replaced by a metal ion.

6. **Conclusion**:
- Since alkynes can undergo electrophilic addition, nucleophilic addition, and substitution reactions (though substitution is rare), the correct answer is that alkynes can participate in all of the above types of reactions.

### Final Answer:
- The type of reactions shown by alkynes are **all of the above** (electrophilic addition, nucleophilic addition, and substitution reactions).