The process of fermentation of milk starts when small amount of curd is added to it.
The correct option is A True
For curd formation to start, milk has to be supplied with a bacteria called Lactobacillus. This bacteria ferments the milk sugar lactose, forming lactic acid. This lactic acid reduces the pH of milk and coagulates it forming curd.
During the process of making curd, small amount of curd is added to boiled milk. This curd acts as an inoculum, supplying the bacteria.