**Explanation:**

**1. Molecular Formula of Alkane:**
Alkanes are hydrocarbons with the general formula CnH2n+2, where 'n' represents the number of carbon atoms in the alkane molecule. Therefore, the molecular formula of the given alkane containing 'm' carbon atoms is CmH2m+2.

**2. Combustion of Alkanes:**
When alkanes undergo combustion, they react with oxygen to produce carbon dioxide (CO2) and water (H2O) as the main products. The balanced chemical equation for the combustion of the alkane can be represented as:

CmH2m+2 + (3m+1/2)O2 → mCO2 + (m+1)H2O

**3. Ratio of Alkane to Water Molecules:**
From the balanced equation, we can see that for every 1 mole of alkane (CmH2m+2), 'm+1' moles of water (H2O) are formed. This means that the number of water molecules formed in the combustion of one mole of alkane is equal to 'm+1'.

**4. Answer:**
Therefore, the correct answer is 4. m - 1, as the number of water molecules formed in the combustion of one mole of alkane containing 'm' carbon atoms is 'm+1'. By subtracting 1 from 'm+1', we get 'm-1', which represents the number of water molecules formed.

2m+2/2 =  m+1