The option which is not a characteristic of chordates is chloroplasts in their cells.
Chordates do have a dorsal supporting rod (vertebrates are types of chordates - they have a spine), a dorsal hollow nerve cord (within the spine), and pharyngeal pouches. However, they do not have chloroplasts, because that is a characteristic of photoautothropic eukaryotes, which chordates certainly are not.
The 3rd one I think not really sure
So we can protect ourselves from the same virus if it attacks again in the future
Because their use is not sustainable because their formation takes billions of years to renew them
