A pipe is to be installed between points A to D$.$ The ground level has been recorded and the required level for the underside of the pipe at point A has been calculated. The pipe must fall at a stated gradient $($the ratio of change in vertical height with horizontal distance, V: H is given in the table below$),$ with the pipe reducing in level from A to D$.$ A traveller $($height provided in the table$)$ is to be used in conjunction with sight rails to ensure the excavation reaches the correct depth and the pipe is installed at the correct fall. The sight rails must be more than $500$mm above the ground but less than $1\mathrm{.}7$m above the ground surface. What is the required height of the sight rail above the ground at point C$,$ and has the condition for the level of sight rails at points A$-$D been achieved $($greater than $500$mm but less than $1\mathrm{.}7$m above the ground surface? a$)$ No$,$ the criteria for the sight rails have not been met. The height of the sight rail at C is $0\mathrm{.}649$m above the ground surface b$)$ No$,$ the criteria for the sight rails have not been met. The height of the sight rail at C is $0\mathrm{.}149$m above the ground surface c$)$ Yes, the criteria for the sight rails have not been met. The height of the sight rail at C is $0\mathrm{.}849$m above the ground surface d$)$ Yes, the criteria for the sight rails have been met. The height of the sight rail at C is $1\mathrm{.}349$m above the ground surface e$)$ none of the above