Final answer:
There is no mistake in the sampling methods listed, but 'Convenient sampling' is more commonly known as 'Convenience sampling', which is a nonrandom method that can lead to biased data.
Step-by-step explanation:
The student has inquired about which line in the given sampling procedure list is mistaken. To clarify, all the options provided (A. Random sampling, B. Systematic sampling, C. Stratified sampling, D. Convenient sampling) are recognized types of sampling procedures. However, the term 'Convenient sampling' is typically referred to as 'Convenience sampling'. Convenience sampling is a nonrandom method that selects individuals that are easily accessible and may result in biased data. The proper methods for random sampling include simple random sampling, stratified sampling, systematic sampling, and cluster sampling. Therefore, the original question does not contain a clear mistake in terms of the listed sampling methods, but rather a potential typo or misrepresentation of 'Convenience sampling'.