Final answer:
The most likely cause of the symptoms is supine hypotension, a condition that occurs when the pregnant uterus compresses the inferior vena cava when the patient is lying flat, leading to reduced blood return to the heart and symptoms of dizziness and weakness.
Step-by-step explanation:
The condition most likely to cause the presentation of a pregnant female in her 24th week of gestation who is experiencing dizziness/weakness with extreme nausea, and who has a high heart rate and low blood pressure without signs of vaginal bleeding, amniotic fluid leakage, or abdominal pain, is C) Supine hypotension. Supine hypotension occurs when the pregnant uterus compresses the inferior vena cava when the patient is in the supine position. This compression can reduce the return of blood to the heart, leading to lowered blood pressure and symptoms like dizziness and weakness. The condition cannot be uterine rupture or spontaneous abortion, as these would likely present with pain and/or bleeding, and the question does not mention placenta previa, which is typically associated with painless vaginal bleeding.