Fertilizers used to lower soil pH (when soil is alkaline) are—

1. $\mathrm{(NH_4)_2SO_4}$
2. $\mathrm{(NH_4)_3PO_4}$
3. $\mathrm{CaO}$

• ai and ii
• bii and iii
• ci and iii
• di, ii and iii