Questions

The    HIV    virus    continuously    invades    and destroys  T-cells  (lymphocytes).  Eventually  the body can't replace the T-cells fast enough, and the  immune  system  deteriorates.  When  the immune  system has deteriorated to the point that it is unable to fight off diseases, a person is diagnosed with AIDS.

In a plant, photosynthesis generally occurs in the leaves part as leaves have chlorophyll which is used for making food using sunlight.

Cost variance is nothing but the difference between the actual incurred cost and the estimated standard cost. This can be occured due to any changes in the volume of goods or services ordered. 

A favorable cost variance occurs when the actual incurred cost is less than the standard cost estimated before the production.