Emery

A sample of an unknown pure substance $x$ is analyzed and found to contain $6\mathrm{.}54g$ of Element $E_1,7\mathrm{.}46g$ of Element $E_2,$ and no other elements.

A similar analysis is made of three other substances that also only contain Elements $E_1$ and $E_2.$ The results are shown in the table below. Decide whether each of the other substances is also a pure substance. If you don't have enough information to decide, choose can't decide.

$\backslash$table$[[$substance$,$mass of $E_1,$mass of $E_2,$pure substance?$],[,,,$pure substance$],[,16\mathrm{.}3g,4\mathrm{.}66g,$mixture$],[($can$\text{'}$t decide$),,,],[B,18\mathrm{.}6g,18\mathrm{.}4g,\backslash$table$[[$pure substance$],[$mixture$],[($can$\text{'}$t decide$)]]],[C,{12\mathrm{.}9}^4,17\mathrm{.}1g,\backslash$table$[[$pure substance$],[$mixture$],[($can$\text{'}$t decide$)]]]]$