A sample of an unknown pure substance $x$ is analyzed and found to contain $4\mathrm{.}67g$ of Element $E_1,5\mathrm{.}33g$ 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$],[,15\mathrm{.}2g,5\mathrm{.}79g,$mixture$],[($can$\text{'}$t decide$),,,],[B,27\mathrm{.}2g,7\mathrm{.}77g,\backslash$table$[[$pure substance$],[$mixture$],[($can$\text{'}$t decide$)]]],[C,25\mathrm{.}5g,14\mathrm{.}5g,\backslash$table$[[$pure substance$],[$mixture$],[($can$\text{'}$t decide$)]]]]$