Identify the transformation

The reaction is: $\mathrm{CH_3CH_2CH_3} \longrightarrow \mathrm{CH_3CH_2CHO}$

That is, propane is being converted to propanal.

What type of reaction is this?

We are converting an alkane into an aldehyde by controlled oxidation: $\mathrm{R-CH_3} \rightarrow \mathrm{R-CHO}$

This is not a common oxidation with strong oxidizing agents, because strong oxidants usually over-oxidize the compound.

Check each reagent

A. Molybdenum oxide

• Higher alkanes can be oxidized in a controlled way using catalysts like molybdenum oxide to give aldehydes.
• Thus propane can give propanal under controlled catalytic oxidation.
• So this is a suitable reagent.

B. Manganese acetate

• This is not the standard reagent for direct conversion of propane to propanal.
• Not correct here.

C. Copper at high temperature and pressure

• Copper is generally used in dehydrogenation of alcohols, e.g. $\mathrm{RCH_2OH} \xrightarrow[573\,K]{Cu} \mathrm{RCHO}$
• But here the starting compound is an alkane, not an alcohol.
• So this is not correct.

D. Potassium permanganate

• $\mathrm{KMnO_4}$ is a strong oxidizing agent.
• It would not selectively stop at aldehyde in such a transformation.
• Hence not correct.

Conclusion

The correct reagent is: $\boxed{\text{A. Molybdenum oxide}}$

Comparison with stored answer

Stored correct answer: A

My derived answer is also A, so they agree.