The formula used to estimate how many homogeneous test questions should be added to a test to raise its reliability to the described level is:

Correct option is B

The Spearman-Brown Prophecy Formula is used to estimate how many homogeneous test questions need to be added to a test to increase its reliability to a desired level. It is particularly useful in situations where a test is lengthened by adding more similar items to improve reliability.

​Information Booster:  $$R=\frac{kr}{1+(k-1)r}$$​

Where:
R = new (desired) reliability coefficient
r = current reliability coefficient
k = factor by which the test length is increased

Additional Information:
-Coefficient Alpha (Cronbach's Alpha): Measures internal consistency of a test but does not estimate how many items need to be added to improve reliability.
-Pearson Product-Moment Correlation: Measures linear relationships between two continuous variables, not test reliability.
-KR-20 (Kuder-Richardson Formula 20): Used for dichotomous (right/wrong) test items to assess internal consistency but does not estimate additional items needed.