The parallax equation $$\Delta {\text{p}} = \frac{{{\text{Bm}}\Delta {\text{h}}}}{{{\text{H}} - {\text{h}}}}$$   is applicable to entire overlap of the photographs only if parallax is measured

A. Normal to base line

B. Parallel to base line

C. Both (A) and (B)

D. Neither (A) nor (B)

Answer: Option B