Which of the following can cause too much heat on the anode and lead to failure?

The correct answer encompasses all of the options listed. Each of these factors can contribute to overheating the anode in an X-ray tube, leading to potential failure.

When excessive exposure is applied to a cold tube, it can cause a rapid increase in temperature that the anode may not handle well. The materials used in the anode are designed to withstand certain temperature thresholds, and sudden exposure can chip away at its integrity.

Additionally, a rapid series of large exposures generates significant heat due to the high intensity and frequency of the X-rays produced. This can overwhelm the heat dissipation capabilities of the anode, increasing the risk of damage.

High milliampere (mA) settings, particularly those greater than 400 mA, also lead to higher tube current, resulting in increased thermal load on the anode. Over time, or with repeated use, this excessive heat can severely compromise the anode's structure.

Thus, all these factors together contribute to the excessive heating and potential failure of the anode in the X-ray machine.