Which of the following is primarily composed of calcium phosphate? Which strong base turns red litmus blue? Match the reaction types with their examples.

93. The correct option is 3). Tooth enamel is primarily composed of calcium phosphate in the form of hydroxyapatite.

94. The correct option is 2). Potassium hydroxide ($\text{KOH}$) is a strong base. Bases turn red litmus paper blue and have no effect on blue litmus paper. Therefore, red litmus turns to blue and blue litmus remains blue.

95. The correct option is 1). Let's match each reaction type:

• a) $\text{Zn}_{(\text{s})} + 2\text{AgNO}_{3(\text{aq})} \rightarrow \text{Zn}(\text{NO}_3)_{2(\text{aq})} + 2\text{Ag}_{(\text{s})}$ This is a displacement reaction where zinc displaces silver from silver nitrate. So, (a) matches with (iii).
• b) $\text{NaCl}_{(\text{s})} + \text{AgNO}_{3(\text{aq})} \rightarrow \text{AgCl}_{(\text{s})} + \text{NaNO}_{3(\text{aq})}$ This is a double displacement reaction where the ions of two compounds exchange places. So, (b) matches with (iv).
• c) $\text{CaCO}_{3(\text{s})} \rightarrow \text{CaO}_{(\text{s})} + \text{CO}_{2(\text{g})}$ This is a decomposition reaction where a single compound breaks down into two or more simpler substances. So, (c) matches with (i).
• d) $\text{Mg}_{(\text{s})} + \text{O}_{2(\text{g})} \rightarrow 2\text{MgO}_{(\text{s})}$ This is a combination reaction where two or more reactants combine to form a single product. So, (d) matches with (ii).

Therefore, the correct matching is (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii).

96. The correct option is 4). To find the value of x, we need to balance the chemical equation:

$$\text{C}_3\text{H}_8 + \text{xO}_2 \rightarrow \text{yCO}_2 + \text{zH}_2\text{O}$$