The atomic number is 49.
The atomic number is the same as the number of protons. So if there are 49 protons, then the atomic number of element A is 49.
There are many factors, but some may include loss of food, loss of sunlight, survival of the fittest, where one species may dominant the other, resulting in the extinction of the weaker species, and changes in the environment, such as climate change.
Answer:
These include your skin, tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils. Pathogenic (disease-causing) microorganisms must make it past this first line of defence. If this defence is broken, the second line of defence within your body is activated.
Explanation: