Identify A to F :
`A overset(LiAIH_4)to C_2H_5OH overset(PBr_3)to B overset(KCN)to Coverset(D)to C_3H_7NH_2 overset(HNO_2)toE overset([O])underset(K_2Cr_2O_7//H^(+))toF`

Explanation

To solve the problem, we need to identify the compounds A to F based on the given reactions. Let's break down the steps:

### Step 1: Identify Compound A
- **Reaction:** A reacts with lithium aluminum hydride (LiAlH4) to give C2H5OH (ethanol).
- **Analysis:** Lithium aluminum hydride is a reducing agent that can reduce aldehydes and ketones to alcohols. Since the product is ethanol, A must be an aldehyde that, when reduced, forms ethanol.
- **Conclusion:** A is **acetaldehyde (CH3CHO)**.

### Step 2: Identify Compound B
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