Final answer:
A Reliable measure accurately measures the variable of interest, while a reliable measure consistently produces a given result. So, the correct answer is option b. Reliable.
Step-by-step explanation:
In the context of data collection, a valid measure needs to accurately measure the variable of interest. Validity refers to the extent to which an instrument or tool accurately measures what it's supposed to measure.
This is different from reliability, which refers to the ability to consistently produce a given result. While any valid measure is by necessity reliable, the reverse is not necessarily true. Researchers strive to use instruments that are both highly reliable and valid.
So, the correct answer is option b. Reliable.