At Boyle's temperature, the value of compressibility factor $Z=\left(P{V}_m/RT=V_{\text{real }}/V_{\text{ideal }}\right)$ has a value of 1, over a wide range of pressure. This is due to the fact that in the van der Waal's equation:

both the constant 'a' and 'b' are negligible

the constant 'b' is negligible and not 'a'

the constant 'a' is negligtble and not 'b'

the effect produced due to the molecular attractions compensates the effect produced due to the molecular volume