Final Answer:
A positive pregnancy test, which detects the presence of human chorionic gonadotropin (hCG), is the only definite sign of pregnancy, offering a direct and reliable confirmation. Other signs such as visualization of the fetus, Goodell sign, and Chadwick sign are indicative but lack the same level of certainty as a positive pregnancy test. Thus the option B) Positive pregnancy test is correct answer.
Step-by-step explanation:
The only definite sign of pregnancy is a positive pregnancy test. This test detects the presence of human chorionic gonadotropin (hCG) in a woman's urine or blood, a hormone produced by the placenta after a fertilized egg attaches to the uterine lining. Visualization of the fetus, Goodell sign, and Chadwick sign are all indicative but not definitive signs of pregnancy. They may suggest pregnancy, but they do not confirm it with the same level of certainty as a positive pregnancy test.
A positive pregnancy test is a reliable indicator as it directly measures the presence of hCG, which is specific to pregnancy. The test typically involves a chemical reaction that produces a visible line or a digital display indicating pregnancy. Other signs, such as visualization of the fetus, may only occur later in pregnancy and are subject to various factors, including the accuracy of imaging technology. Therefore, while these signs may strongly suggest pregnancy, they lack the definitive confirmation provided by a positive pregnancy test.
In summary, a positive pregnancy test is the gold standard for confirming pregnancy as it directly detects the presence of hCG, the hormone produced during pregnancy. This method is more conclusive than relying on physical signs or imaging, providing a clear and reliable indication of pregnancy status.