The decreasing leaving group order (fugacity order) of the following compounds is:
i. `H_(2)O`, ii. `H_(2)S`, iii. `H_(2)Se`, iv. `H_(2)Te`

Options

A. `(i) gt (ii) gt (iii) gt (iv)`
B. `(iv) gt (iii) gt (ii) gt (i)`
C. `(iiii) gt (i) gt (ii) gt (iv)`
D. `(iv) gt (ii) gt (i) gt (iii)`

Explanation

To determine the decreasing order of leaving groups (fugacity order) for the compounds \(H_2O\), \(H_2S\), \(H_2Se\), and \(H_2Te\), we will analyze their basic strengths. The key concept here is that the stronger the base, the weaker the leaving group. Therefore, the order of leaving groups will be the reverse of the order of basicity.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have the following group 16 hydrides:
- \(H_2O\) (water)
- \(H_2S\) (hydrogen sulfide)
- \(H_2Se\) (hydrogen selenide)
- \(H_2Te\) (hydrogen telluride)

2. **Understand Basicity**: Basicity is the ability of a compound to donate a lone pair of electrons. In this case, all these compounds can act as Lewis bases because they have lone pairs on the central atom (O, S, Se, Te).

3. **Analyze the Trend in Basicity**: As we move down the group from oxygen to tellurium, the size of the central atom increases. This increase in size leads to a decrease in electron density, which in turn decreases the basicity of the compounds. Therefore, the basicity order is:
- \(H_2O > H_2S > H_2Se > H_2Te\)

4. **Determine the Leaving Group Order**: Since the leaving group ability is inversely related to basicity, we reverse the order of basicity to get the leaving group order:
- \(H_2Te > H_2Se > H_2S > H_2O\)

5. **Final Order**: Thus, the decreasing order of leaving groups (fugacity order) is:
- \(H_2Te > H_2Se > H_2S > H_2O\)

### Conclusion:
The correct answer for the decreasing leaving group order is:
- \(H_2Te > H_2Se > H_2S > H_2O\)