Sampling in which sampling units are selected on the advice of some experts or by the intuition or opinion of the researcher himself is known as:

Correct option is A

Judgment sampling, also known as purposive sampling, is a type of non-probability sampling where the researcher uses their judgment or expert opinion to select the sampling units that they believe are most appropriate for the study. This method involves selecting individuals who are most likely to provide valuable insights based on the research objectives.

Information Booster:

1. Judgment sampling allows researchers to select participants who are expected to have specific characteristics or experiences relevant to the research.
2. It is often used when there is limited access to the entire population or when the researcher has a strong understanding of the subject matter.
3. This technique is especially useful in qualitative research where deep insights are more important than generalizing findings.
4. Expert opinion in judgment sampling can guide the researcher in selecting key individuals who may have specific knowledge or experience related to the study topic.
   

Additional Knowledge:

• Snowball sampling: A technique where existing participants refer new participants to the study, often used when studying hard-to-reach populations.
• Quota sampling: A type of non-probability sampling where the researcher ensures certain characteristics are represented in the sample in a predefined way, without using random selection.
• Convenience sampling: A non-probability sampling method where the researcher selects units that are easiest to access, often leading to biases.