A. <span>Exposure to an antigen
Exposure to viruses and antigens led to the foundation of modern vaccination. Vaccination introduces an antigenic material that helps the ability of the immune system to adapt a specific pathogen, therefore leading to a long-term immunity.</span>
A particular single-celled organism uses radiant energy to fix carbon as sugars. This organism generates ATP by breaking down sugars through a process that uses oxygen. This organism is aerobic autotroph.
Autotrophs produce their own food from the substances available in their surroundings using light through photosynthesis or chemo-synthesis.
The answer above is incorrect. The correct answer is James Watson accompanied by Francis Crick.
The correct answer is A. Decline in vision
Explanation:
The term "middle age" is used to describe the time span between 45 and around 65 in human life. During this, important changes occur in terms of senses, this age usually implies a decline in senses including pain, taste, smell, and vision. In terms of vision, it is common during middle ages people began experiencing blurring vision or weakened vision as during this age conditions such as presbyopia, glaucoma, cataracts, among others. Additionally, the decline in vision in this age is commonly related to other conditions such as diabetes, the use of medicines and also jobs that are visually demanding. Thus, in middle age, people commonly experience a decline in vision.
