A critical weld was made with a double V-groove. Among those listed, which radiographic technique would provide coverage with the greatest probability for detecting the most serious discontinuities?

) A single exposure centered on the weld and perpendicular to the principal surface of the plate

Two exposures aligned with the V-groove focus, +30° off perpendicular

Two exposures, perpendicular to the plate, offset by the width of the weld bead.

A single exposure as in a, above, but with two films aligned ±30° off perpendicular.

Both a and d would produce the best coverage.