Question

Look at the graph below. Which elements together make up seven percent of the Earth’s crust? calcium and iron calcium and sodium potassium and magnesium potassium and sodium

Answer 1

The graph is missing, however we can answer anyway.

In fact, this is the approximate percentage of the elements listed in the questions in the Earth's crust (data taken from wikipedia):
Iron 5.0 %
Calcium 3.6 %
Sodium 2.8 %
Potassium 2.6 %
Magnesium 1.5 %

of all of these, we see that the combination of two elements that makes up the closest number to 7% is calcium and sodium (3.6% + 2.8%=6.4%), therefore the correct answer is
Calcium and sodium.