The rate of decomposition of hydrogen peroxide (H$_2$O$_2$ $\longrightarrow$ H$_2$O + O$_2$), which is slow at room temperature, can be increased by adding:

1. Hydrogen peroxide decomposes slowly into water and oxygen at room temperature. 2. Adding manganese dioxide (MnO$_2$) powder speeds up the reaction; MnO$_2$ acts as a catalyst. 3. MnO$_2$ increases the rate without itself undergoing chemical change. 4. NaCl, CaCO$_3$ and KNO$_3$ are not catalysts for this decomposition, so those options are wrong. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 3 "Chemical Reactions and Equations", p.50_