What’s the correct answer !!

From my side the correct option is "A"

Explanation:    Reasons for its correction are ,

1)  Highly reactive: Nanoparticles are therefore extremely unstable and easily change themselves or react with active substances to reach a relatively stable state in some cases. This causes desired changes or undesired changes to nanoparticles and thus makes them exhibit a high reactivity and a poor stability.

2)Small size:  Nanotechnology can provide rapid and sensitive detection of cancer-related molecules, enabling scientists to detect molecular changes even when they occur only in a small percentage of cells. Nanotechnology also has the potential to generate entirely novel and highly effective therapeutic agents.

108.43 grams KNO₃

Explanation:

To solve this problem we use the formula:

ΔT = Kf * b * i

Where

ΔT is the temperature difference (14.5 K)Kf is the cryoscopic constant (1.86 K·m⁻¹)b is the molality of the solution (moles KNO₃ per kg of water)and i is the van't Hoff factor (2 for KNO₃)

We solve for b:

14.5 K = 1.86 K·m⁻¹ * b * 2b = 3.90 m

Using the given volume of water and its density (aprx. 1 g/mL) we calculate the necessary moles of KNO₃:

275 mL water ≅ 275 g water275 g /1000 = 0.275 kgmoles KNO₃ = molality * kg water = 3.90 * 0.275moles KNO₃ = 1.0725 moles KNO₃

Finally we convert KNO₃ moles to grams, using its molecular weight:

1.0725 moles KNO₃ * 101.103 g/mol = 108.43 grams KNO₃