Strategies to effectively answer multiple-choice questions in Paper I of UPSC Chemistry Optional subject:

1. Understand the question:
- Read the question carefully to understand what is being asked.
- Identify the key terms and concepts mentioned in the question.

2. Review the options:
- Read all the options before selecting an answer.
- Eliminate the options that are clearly incorrect or unrelated to the question.

3. Use the process of elimination:
- Analyze each option and eliminate the ones that are obviously incorrect.
- Look for clues within the question that may help eliminate certain options.
- Cross out the eliminated options to narrow down the choices.

4. Prioritize the options:
- In some cases, multiple options may seem correct. Prioritize them by determining which option is the most accurate or comprehensive.
- Consider the logical flow or sequence of the answer options.

5. Use your knowledge:
- Draw upon your understanding of the subject matter to make an informed decision.
- Apply relevant concepts, principles, and theories to arrive at the correct answer.

6. Use the process of approximation:
- If you are unable to determine the exact answer, use the process of approximation to select the closest option.
- Consider the given range of values and select the option that falls within that range.

7. Manage your time:
- Allocate a specific amount of time for each question and stick to it.
- If you are unsure about an answer, make an educated guess and move on to the next question to avoid wasting time.

8. Review your answers:
- Once you have answered all the questions, review your answers to ensure accuracy.
- Double-check any questions that you were unsure about or guessed.

Remember, it is important to thoroughly prepare for the UPSC Chemistry Optional subject by studying the relevant topics, practicing previous years' question papers, and seeking guidance from qualified mentors.