Which of the following is a common symptom of pregnancy according to presumptive signs?

Amenorrhea is considered a common presumptive sign of pregnancy because it refers to the absence of menstruation. This symptom is often one of the first indicators that a woman might be pregnant, as many women notice that their menstrual cycle has stopped or is irregular shortly after conception. The absence of menstruation is typically due to hormonal changes that occur once implantation of the embryo happens and the body begins to sustain the pregnancy.

In the context of pregnancy, presumptive signs are those signs that could possibly indicate pregnancy but are not definitive. Amenorrhea fits this category well, as it can occur for other reasons, such as stress, hormonal imbalances, or significant weight changes.

While a positive pregnancy test and visual fetal heartbeat are also pivotal for confirming pregnancy, they are not classified as presumptive signs. A positive pregnancy test indicates hormonal changes due to pregnancy, and visualizing the fetal heartbeat typically occurs during an ultrasound later in the pregnancy. Severe headaches can occur for numerous reasons and are not a typical direct indication of pregnancy, making amenorrhea the most common presumptive sign listed.