Which of the following are deductions？

A、All dogs are mammals. All mammals have kidneys. Therefore all dogs have kidneys.

B、Since all squares are rectangles, and all rectangles have four sides, all squares have four sides.

C、All science teachers are smart, since all my physics teachers, chemistry teachers and biology teachers are smart.

D、The sun is a star; the sun has planets; therefore some stars have planets.

正确答案：All dogs are mammals. All mammals have kidneys. Therefore all dogs have kidneys.#Since all squares are rectangles, and all rectangles have four sides, all squares have four sides.#The sun is a star; the sun has planets; therefore some stars have planets.