Tam a highly reactive alkali metal in period 3 with only one valence electron O Sodium (Na)
Beryllium (Be)
Magnesium (Mg)

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.