Option 1 states that both the assertion (A) and the reason (R) are individually true, and R is the correct explanation of A. Let`s analyze each statement separately:

Assertion (A) states that red blood cells burst when placed in water. This statement is true. Red blood cells have a higher concentration of solutes compared to pure water, so when they are placed in water, water molecules enter the cells through a process called osmosis. As water enters the cells, they swell up and eventually burst, leading to cell lysis.

Reason (R) states that due to osmosis, water enters into red blood cells. This statement is also true. Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration through a semipermeable membrane. In this case, the red blood cells have a higher concentration of solutes compared to the water, so water molecules enter the cells to equalize the solute concentration.

Therefore, option 1 is correct because both the assertion and reason are true, and the reason correctly explains the assertion. No alert is needed as the provided answer is correct.