The first line of defence (or outside defence system) includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These include your skin, tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils.
Answer:
The beaver population increased
Explanation:
under what circumstance does a negative cell presents An antigen to another negative cell
This question is incomplete; here is the complete question:
_____ is work done to keep equipment in good working order.
A. Defragmentation
B. Preventive maintenance
C. Virus protection
D. A maintenance schedule
The correct answer is B. Preventive maintenance
Explanation:
Maintenance refers to the processes done on machinery or equipment to preserve its proper functioning. Moreover, this maintenance is preventive if it is done to prevent equipment from breaking down or having any malfunctioning. Besides this, preventive maintenance is globally recommended because in this way equipment used at home or in business works properly. According to this, the correct answer is preventive maintenance.