Which of the following is a positively charged sol?

The correct answer is Option (4) → Blood

Colloidal particles always carry an electric charge, and the sign of the charge depends on the substance. Haemoglobin (blood) forms a positively charged sol, like the sols of hydrated metallic oxides and basic dyes. Starch, gum and metal sols such as gold sol are negatively charged.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Properties of Colloidal Solutions – …