An element (which is written as a X) makes the compositions X2O and XO. Which compositions it is gonna make with chlorine? a) XCl and XCl2
b) XCl2 and XCl3
c) XCl and XCl3

i believe it is 40–40–20%

explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.