When blood cells are placed in 1% (w/v) NaCl aquem solution:

The correct option is "Cell will shrink".

To understand why this happens, we need to look at the concentration of solutes inside and outside the red blood cells (RBCs) and the process of osmosis.

Red blood cells naturally contain a fluid that has an osmotic concentration equivalent to a 0.9% (w/v) sodium chloride (NaCl) solution. This concentration is considered isotonic to the cell cytoplasm, meaning the rate of water entering the cell is equal to the rate of water leaving it, maintaining the cell's normal shape and volume.

When blood cells are placed in a 1% (w/v) NaCl solution, they are placed in a hypertonic environment because 1% is a higher solute concentration than the 0.9% concentration inside the cells.

Osmosis is the net movement of water molecules from a region of lower solute concentration (higher water potential) to a region of higher solute concentration (lower water potential) across a selectively permeable membrane.

Due to this concentration gradient, water moves out of the red blood cells into the surrounding 1% NaCl solution. This outward movement of water (exosmosis) causes the cells to lose volume, leading to their shrinkage (a process known as crenation).