Identify the properties of the substance to be extracted

The question states that essential oils:

• are steam volatile,
• are insoluble in water at room temperature,
• but are miscible with water vapour in the vapour phase.

These are exactly the conditions under which steam distillation is used.

Recall the principle of steam distillation

Steam distillation is used for compounds which:

• are volatile in steam,
• are immiscible or only slightly soluble in water,
• may decompose if heated strongly at their normal boiling point.

In this method, the organic compound co-distils with water at a temperature lower than its normal boiling point.

Evaluate the options

A: Distillation

• Simple distillation is used for liquids that boil without decomposition and can be directly heated.
• Essential oils from flowers are generally extracted using steam, not ordinary distillation.
• Incorrect.

B: Steam distillation

• This is specifically suitable for steam volatile, water-insoluble organic compounds, such as essential oils.
• Correct.

C: Distillation under reduced pressure

• This is used for liquids with high boiling points or substances that decompose on strong heating.
• Although useful in some cases, the key property given here is steam volatility, which points directly to steam distillation.
• Incorrect.

D: Crystallisation

• Crystallisation is used for purification of solids, not for extracting volatile oils from flowers.
• Incorrect.

Final answer

The suitable method is: $\boxed{\text{B: Steam distillation}}$

Comparison with stored correct answer

Stored correct answer: B

My derived answer: B

Hence, they agree.