Which of the following statements about the excretory system of insects is not true?

• A. Active transport moves materials from the coelomic fluid into the Malpighian tubules.
• B. The Malpighian tubules can produce a highly concentrated urea solution, allowing insects to inhabit some of Earth's driest habitats.
• C. Reabsorption of salts takes place mostly in the gut.
• D. Water reabsorption is by osmotic movement only.