Note : first physical quantity is along y-axis
A) : Isobaric process means that P=constant
Thus P-T graph will be a straight line parallel to T axis.
Hence option 2 is correct.
C) : P=constant ⟹T∝V (from ideal gas equation)
Thus T-V graph will be a straight line passing through origin and having a finite slope.
Hence option 1 is correct.
D) : For isobaric process, T∝V
But ρ∝1V ⟹ Tρ=constant
Thus T- ρ will be a curved line.
Hence option 3 is correct.
B) U=nCvT
Thus U-ρ graph is similar to T−ρ graph
Hence option 3 is correct.