The correct answer is option 2: weakly alkaline.

When a milkman adds a small amount of baking soda to milk, it increases the alkalinity of the milk. Baking soda, also known as sodium bicarbonate, is a basic compound. It has a high pH value, which means it is alkaline.

Milk itself is slightly acidic, with a pH value ranging from 6.4 to 6.8. When baking soda is added to milk, it reacts with the acidic components of milk and increases the pH of the milk. However, the increase in pH is not significant enough to make the milk strongly alkaline.

Therefore, the milk becomes weakly alkaline after the addition of baking soda. This can have various effects on the milk, such as increasing its shelf life by inhibiting the growth of certain bacteria. It can also affect the taste and texture of the milk.