Concept:The angle between two lines is found using their direction ratios and the dot product formula.Explanation:The line x=y,z=0 can be written as 1x=1y,z=0, so its direction ratios are (1,1,0).The line y=0,z=0 is the x-axis, so its direction ratios are (1,0,0).If θ is the angle between the lines, thencosθ=12+12+0212+02+02(1)(1)+(1)(0)+(0)(0)=21Therefore, θ=45∘.Answer:The angle between the lines is 45∘, i.e., option B.