Which of these always remains unchanged over time? a: the understanding of how diseases affect people b: the way in which diseases are treated c: the number of people who have diseases d: the causes of human diseases

Option D, the causes of human diseases

Explanation:

Most of the diseases are caused by microbes and the remaining are caused by other agents such as animals bite, etc.

Specific microbes causing specific diseases affects always remains the same. For example if salmonella Typhi causes typhoid diseases, then causative agent will remain same. However, the way our body responds to such microbes may change in long run.

Thus, the symptoms of a disease may change, the number of people effected by a disease may change and even the the understanding of how diseases affect people may change but the causative agent i.e cause of human disease remains the same.

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.