The enzyme that breaks down lactose is: MCQ with Answer and Explanation

Explanation:
Veins carry blood back to the heart under low pressure and have one-way valves that prevent backflow. Skeletal muscle contractions also assist venous return.

Explanation:
Syphilis is caused by the spirochete Treponema pallidum and is curable with antibiotics. Hepatitis B and HIV are viral, genital herpes is caused by herpes simplex virus. Gonorrhea and chlamydia are other bacterial STDs. Early diagnosis and treatment prevent serious complications like neurological damage and congenital syphilis.

Explanation:
Charles Darwin proposed the theory of evolution by natural selection, emphasizing that organisms with favorable variations are more likely to survive and reproduce. Hugo de Vries, a Dutch botanist, proposed the mutation theory of evolution based on his work on evening primrose, stating that evolution occurs through sudden, large mutations (saltations). Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characters, based on the use and disuse of organs (e.g., giraffe's neck). All statements are correct.