The correct answer is:
_________________________________________________________
" F and Br , because they are in the same group" .
_________________________________________________________
Note:
_________________________________________________________
Choice [B]: "F and Br ; because they are in the same period" ; is incorrect; since "F" and "Br" are not in the same "period" (that is, "row").
______________________________________________________
Choice [C]: "Na and Mg; because they are in the same group {"column"} ; is incorrect; since: "Na" and "Mg are NOT in the same group {"column"].
_______________________________________________________
Choice [D]: "Na and Mg" ; because they are in the same period {"row"}; is incorrect. Note: "Na" and "Mg" are, in fact, in the same period {"row"}. However, as aforementioned, {Mg and Na} are not in the same group {"column".}.
Note: The similiarities in physical and chemistry properties among elements are determined and organized — or tend to be so—by "groups" {"columns"} — NOT by "periods" {rows}.
______________________________________________________
Answer:

Explanation:
Hello,
In this case, given that a typical aspirin tablet contains 5.00 grains of pure aspirin, the first step here is to compute the mass of those grans per tablet given that 1.00 g = 15.4 grains:

In such a way, the number of aspirin tablets are computed considering the total mass of aspirin and the mass per tablet:

Best regards.
Any substance that is not a mixture is a pure substance. When colored watercolors are applied to paper, sometimes the colors in the ink separate. This technique is called chromatography