If there are similar charges on colloidal particles, neutralization does not take place and the colloid becomes stable. So, option (B) is correct. Brownian movement helps to counter the force of gravity acting on colloidal particles and thus doesn't allow them to settle down. Therefore, option (D) is also correct. When two oppositely charged sols are mixed, coagulation takes place due to neutralization. So, option (A) is wrong. When dispersed phase is added in excess, it forms a separate layer and thus the emulsion gets destabilized. So, option (C) is also wrong.