Why is it necessary to add a day to the calendar every four years? A. The rotation of the Earth is actually 24 hours and 6 seconds.
B. The revolution of the Earth is actually 365.25 days not 365 days.
C. The Earth's orbit is elliptical and not circular.
D. The Earth's axis is tilted and slows its rotation.

B. .25 x 4 equals one. Which is that one day we add.

B. The revolution of the Earth is actually 365.25 days not 365 days.

Some viruses cause infected cells to lyse.  Lysis is the dissolving of the cell by factors like viral, enzymic, or osmosis. Lysis in medical term also means a presence of symptoms of complicated or acute diseases. Example of this disease is the tumor lysis syndrome.