Informed consent must always be:

Informed consent is a fundamental principle in research ethics that ensures participants are fully aware of what their involvement in a study entails, including any risks, benefits, and procedures involved. The correct answer emphasizes that informed consent must be clear and understandable to participants. This clarity is critical for ensuring that individuals can make informed decisions about whether to participate in research.

When consent is clear and understandable, it respects the autonomy of the participants and allows them to comprehend the implications of their participation fully. This includes understanding the nature of the research, the extent of their involvement, any associated risks, and their right to withdraw from the study at any time without any penalty. If the information is too technical or complex, or if it is not presented in a language or manner comprehensible to the participants, the essence of informed consent is undermined. Therefore, clarity and comprehensibility are essential components of a valid informed consent process.

The other options do address aspects related to informed consent, but they lack the fundamental necessity of clarity and understanding in the consent process. For example, while documenting consent in writing can be important in many situations, it is not universally required, especially in certain low-risk studies or where verbal consent is acceptable. Similarly, reaffirming consent at each session