With the horizontal cross dial reading, you zero the _______ o'clock reading on dial B and the _________ o'clock reading on dial A.

In the context of using a horizontal cross dial for alignment tasks, the correct choice involves zeroing the 3 o'clock reading on dial B and the 9 o'clock reading on dial A. This configuration allows for precise measurements when aligning machinery, as it helps to center the readings based on the placement of the dials relative to the machinery being aligned.

The 3 o'clock position on dial B typically indicates a point where measurements can easily be taken without obstruction, while the 9 o'clock position on dial A serves a complementary role in ensuring the symmetry and accuracy of the readings. When both dials are zeroed at these specific positions, it sets a clear reference for subsequent measurements, enabling the millwright to accurately assess any misalignment and make the necessary adjustments.

Utilizing this standard configuration also streamlines communication and documentation of measurements within the workplace, as it is commonly taught and understood among professionals in the field. This consistency is crucial for ensuring that alignment tasks are performed correctly and efficiently.