Step 1: Understanding the Question:
This question tests knowledge of sampling terminology.
Step 2: Detailed Explanation:
The ratio of the sample size to the total population size is called the sampling fraction.
It is denoted as f = n/N.
Sampling unit (A): The individual element being sampled.
Partial sampling (B): Not a standard term.
Sample inventory (C): Not a standard term.
Thus, the correct answer is sampling fraction.
Step 3: Final Answer:
Thus, the ratio of sample to population is the sampling fraction, which corresponds to option (D).
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