Assertion : Montreal protocol, was signed at Montreal (Canada) in 1987 to control the emission of ozone depleting substances.
Reason : Kyoto protocol, held in Kyoto (Japan) in 1987, has specified the commitments of different countries to mitigate climate change.

Options

A. (a) Both, Assertion and Reason, are true and Reason is the correct explanation of Assertion
B. (b) Both, Assertion and Reason, are true but Reason is not the correct explanation of Assertion
C. (c) If Assertion is true but Reason is false
D. (d) If Assertion is false but Reason is true

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the Montreal Protocol was signed in 1987 in Montreal, Canada, to control the emission of ozone-depleting substances.
- This is true as the Montreal Protocol specifically aimed to phase out substances that harm the ozone layer, such as chlorofluorocarbons (CFCs) and other related chemicals.

2. **Understanding the Reason**:
- The reason states that the Kyoto Protocol was held in Kyoto, Japan, in 1987 and specified commitments of different countries to mitigate climate change.
- However, this statement is partially incorrect. The Kyoto Protocol was indeed aimed at addressing climate change, but it was adopted in 1997, not 1987.

3. **Evaluating the Truth of Both Statements**:
- Both the assertion and the reason are true in their own contexts, but the reason does not accurately explain the assertion. The Montreal Protocol is focused on ozone depletion, while the Kyoto Protocol addresses climate change.

4. **Conclusion**:
- Since both statements are true but the reason does not provide a correct explanation for the assertion, the answer is that both the assertion and reason are true, but the reason is not the correct explanation for the assertion.

5. **Final Answer**:
- The correct option is B: Both assertion and reason are true, but the reason is not the correct explanation for the assertion.