Condition for iodoform test

A compound gives a positive iodoform test with $I_2/NaOH$ if it contains either:

• a methyl ketone group: $RCOCH_3$, or
• a secondary alcohol of type: $RCH(OH)CH_3$

because such alcohols are oxidized under the reaction conditions to methyl ketones.

Check each option

From the given options, the visible structures are:

• B: $PhCH(OH)CH_3$
• C: $CH_3CH_2CH(OH)CH_2CH_3$
• D: $C_6H_5CH_2CH_2OH$

(Option A is blank in the prompt, so we evaluate the listed structures.)

Option B: $PhCH(OH)CH_3$

This is a secondary alcohol of the type: $RCH(OH)CH_3$ where $R = Ph$.

On oxidation, it forms: $PhCOCH_3$ which is a methyl ketone.

Therefore, it gives a positive iodoform test.

Option C: $CH_3CH_2CH(OH)CH_2CH_3$

This is 3-pentanol. The carbon bearing $OH$ is attached to two ethyl groups: $CH_3CH_2CH(OH)CH_2CH_3$

It is not of the form $RCH(OH)CH_3$. On oxidation it gives pentan-3-one: $CH_3CH_2COCH_2CH_3$ which is not a methyl ketone.

So, negative iodoform test.

Option D: $C_6H_5CH_2CH_2OH$

This is a primary alcohol. It is not ethanol and not of the required form.

So, it does not give iodoform test.

Conclusion

The compound that gives positive iodoform test is: $\boxed{B}$