To determine which of the following options does not obey the law of reciprocal proportion, we need to understand what the law states and analyze each option accordingly.

The law of reciprocal proportion, also known as Richter's law, states that when two or more elements combine separately with the same fixed mass of another element, the ratios in which they combine with the other element will either be the same or simple whole-number multiples of each other.

Let's analyze each option:

(A) NaH, NaCl, HCl:
- NaH: Sodium (Na) combines with hydrogen (H) to form sodium hydride.
- NaCl: Sodium (Na) combines with chlorine (Cl) to form sodium chloride.
- HCl: Hydrogen (H) combines with chlorine (Cl) to form hydrochloric acid.

In this case, the law of reciprocal proportion is obeyed. Sodium combines with hydrogen and chlorine in fixed ratios.

(B) H2S, H2O, SO2:
- H2S: Hydrogen (H) combines with sulfur (S) to form hydrogen sulfide.
- H2O: Hydrogen (H) combines with oxygen (O) to form water.
- SO2: Sulfur (S) combines with oxygen (O) to form sulfur dioxide.

In this case, the law of reciprocal proportion is obeyed. Hydrogen combines with sulfur and oxygen in fixed ratios.

(C) CH4, H2O, CO2:
- CH4: Carbon (C) combines with hydrogen (H) to form methane.
- H2O: Hydrogen (H) combines with oxygen (O) to form water.
- CO2: Carbon (C) combines with oxygen (O) to form carbon dioxide.

In this case, the law of reciprocal proportion is obeyed. Carbon combines with hydrogen and oxygen in fixed ratios.

(D) PH3, P2O5, H3PO4:
- PH3: Phosphorus (P) combines with hydrogen (H) to form phosphine.
- P2O5: Phosphorus (P) combines with oxygen (O) to form phosphorus pentoxide.
- H3PO4: Hydrogen (H) combines with phosphorus (P) and oxygen (O) to form phosphoric acid.

In this case, the law of reciprocal proportion is not obeyed. The ratio of phosphorus to oxygen in phosphine and phosphoric acid is not a simple whole-number multiple, indicating a violation of the law.

Therefore, the correct answer is option (D) PH3, P2O5, H3PO4, as it does not obey the law of reciprocal proportion.

CH4,H2O,CO2