Help?? Need this for a test

Consider the four elements above. which one of these elements will combine with oxygen in a 1: 1 ratio?

Which of these statements best explains why space exploration should be encouraged? it prepares humans to live without oxygen. it dispel myths about objects in space. it prevents comets and asteroids from striking earth. it creates technology to absorb harmful radiations in space.

The sum of the oxidation numbers in a neutral compound is always