Rapid test and PCR test for Covid are ------- for international travellers and PCR test and international travel at Canada are ------ for international travellers.

a.

They are always substitutes regardless of the purpose of the individual who is taking the test, complement

b.

Could be substitutes depending on the purpose of the individual who is taking the test, substitutes

c.

Complement, substitutes

d.

Could be substitutes depending on the purpose of the individual who is taking the test, complement