4. For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Cells can be very diverse in size, shape, and function. Superficially, they come in various sizes, ranging from bacterial cells such as Escherichia coli, which is a few in length, to larger cells such as a frog’s egg, which has a diameter of about one . Common to all cells, are the , which delimit the cells and provide a selective barrier. Despite their diversity, cells resemble each other to an astonishing degree in their chemistry. For example, the same twenty are used to make proteins. Similarly, the genetic information of all cells is stored in their . An exception to this rule is that some viruses such as HIV their genes are encoded in single strands of .