Which word is correctly used in blank #2?

there __1__ two apartments for sale in this building which going to look at if we can only remember they're located.

a. where
b. were
c. we're

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).

option c is the correct answer.