**Core Concept**
The Medical Termination of Pregnancy (MTP) Act, 1971, regulates the termination of pregnancy in India. The Act requires certain conditions to be met before an MTP can be performed, including the number of previous pregnancies.

**Why the Correct Answer is Right**
The MTP Act, 1971, specifies that an MTP can be performed only if the number of previous pregnancies is at least two. This is a key criterion for the doctor to consider before performing an MTP. The Act aims to prevent the misuse of MTPs and ensure that the procedure is performed only in cases of genuine medical necessity.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the MTP Act does not specify a minimum number of previous pregnancies as one. Performing an MTP with only one previous pregnancy may not meet the criteria set by the Act.
* **Option B:** This option is incorrect because it is not a valid criterion for performing an MTP. The Act does not specify a minimum number of previous pregnancies as two and a half.
* **Option C:** This option is incorrect because it is not a valid criterion for performing an MTP. The Act does not specify a minimum number of previous pregnancies as three.

**Clinical Pearl / High-Yield Fact**
Doctors performing MTPs must ensure that they meet the criteria set by the MTP Act, 1971, to avoid legal and professional repercussions. A key criterion is the number of previous pregnancies, which must be at least two.

**Correct Answer: A. Two**