What do we mean by a blueshift?

Question $10$ options:

$1)$

A Doppler shift caused by an object moving farther away from the observer.

$2)$

A Doppler shift caused by an object getting closer to the observer.

$3)$

A Doppler shift causing the observed wavelength to appear longer than the emitted wavelength.

$4)$

A Doppler shift causing the observed frequency to appear lower than the emitted frequency.

$5)$

A Doppler shift occurring only to the blue end of the visible band wavelengths.

$6)$

A Doppler shift occurring only to the red end of the visible band of wavelengths.