It is D, Because cells are a very complex organism, they have a lot to do. It is like saying you have a play house.. but it is completely empty, that is if you chose A. They were not discovered in 1700s, they were discovered in 1665. and organisms are found in ponds, so they have cells too. So your answer is D.
Which of these is true of cells? A. They are much like empty rooms. B. They were first discovered in the 1700s. C. They cannot be found in pond water. D. They contain a huge array of working parts.