4 When is the adaptive immune system active

А All the time
B Only when there's a repeat infection
C Only after pathogens start to multiply
D Only when a person acquires autoimmunity

Explanation:

Adaptive immunity is an immunity that occurs after exposure to an antigen either from a pathogen or a vaccination. This part of the immune system is activated when the innate immune response is insufficient to control an infection.

the endomembrane system is a series of compartments that work together to package, label, and ship proteins and molecules. in your cells, the endomembrane system is made up of both the endoplasmic reticulum and the golgi apparatus. these compartments are folds of membranes that form tubes and sacs in your cells.

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.