A. False. Some 4 sided shapes could be figures such as trapezoids where only one pair of opposite sides are parallel.
B. True. Some rectangles are squares. Specifically when all four sides are the same length.
C. True. A square is a combination of a rhombus and a rectangle. If the figure is a square, then it is a rhombus and it is also a rectangle.
D. False. Trapezoids only have one pair of opposite parallel sides
-------------------------
In summary, the true statements are choice B and choice C