Explanation:

Let’s break down section 159 of the CrPC and the options:

- The section lets a Magistrate, on receiving a police report under section 157, do one of two things.

- First, they can direct the police to investigate further.

- Second, they can assign any subordinate Magistrate to carry out a preliminary inquiry in person.

- So, it’s not just about police investigation, and it’s not just about deputing another Magistrate—it’s definitely either one or the other, depending on what the main Magistrate thinks is needed.

- Let’s look at the options:

- Option 1: Direct investigation by police. Part of it, but not the whole picture.

- Option 2: Depute any subordinate Magistrate. Also allowed, but again, only half the story.

- Option 3: Either (a) or (b). This is the most accurate—both options are available, not just one.

- Option 4: Only (b), not (a). Not correct, ignores half the Magistrate’s power here.

So, the correct answer is:

Option 3: Either (a) or (b).