To check the height of multiple parts with gage blocks, a machinist would use a:

The correct choice emphasizes the use of a dial indicator and a digital height gage for checking the height of multiple parts with gage blocks. A dial indicator is particularly effective for providing precise readings and can be used to measure small variations in height with a high degree of accuracy, making it suitable for evaluating the heights of machined parts.

When used in conjunction with a digital height gage, which offers electronic measurement capabilities and often includes a display for easy reading, this combination allows machinists to achieve reliable and repeatable results. The digital height gage can be set to specific reference points, and the dial indicator can provide quick feedback on height adjustments.

In contrast, the other options include tools that may not be as well-suited for achieving the precision needed when measuring parts that require high accuracy or may not be designed specifically for height measurement tasks. For example, while calipers and rulers provide basic measurements, they are generally not as precise or user-friendly for measuring heights in multiple setups as the combination of a dial indicator and digital height gage.