The question asks:

How many halobenzenes can be prepared by Sandmeyer’s reaction?

Since the image/list of compounds is not shown, we interpret this as asking which halobenzenes are obtainable from benzene diazonium salt via Sandmeyer reaction.

1. Recall Sandmeyer reaction

Aryl diazonium salts react with cuprous salts to replace the diazonium group by certain halogens:

Also,

For halobenzenes specifically, Sandmeyer reaction directly prepares:

1. Chlorobenzene
2. Bromobenzene

2. Check other halo derivatives

• Iodobenzene is generally prepared from diazonium salt using KI, but this is not Sandmeyer reaction because it does not require cuprous salt.
• Fluorobenzene is prepared by Balz–Schiemann reaction, not Sandmeyer.

So among halobenzenes, only:

• $C_6H_5Cl$
• $C_6H_5Br$

are prepared by Sandmeyer reaction.

3. Count

Therefore, the number of halobenzenes obtainable by Sandmeyer reaction is

4. Comparison with stored answer

Stored correct answer = 2

Our derived answer = 2

So they agree.