This step gives an investigation a specific direction or focus a. observation
b. question
c. hypothesis
d. analysis

The correct answer will be option-C.

Explanation:

A scientific investigation is performed to answer and explain any natural phenomenon or event.  

Any scientific investigation can be performed by following the scientific method which includes many sequential steps which begin with making an observation, asking a question, do background research, propose a hypothesis which can be tested with experiments.

The main focus of any scientific investigation begins after proposing a well educated guess called hypothesis. A hypothesis is constructed on the basis of previous work due to which it explains the phenomenon to a limited extent which has to be tested.  

Thus, a hypothesis gives a direction and is the focus of a scientific investigation and is the correct answer.

beta decay is the answer

i do not get it   at all