The decreasing nucleophilic oder of the following compounds is:
i. `overset(o-)(C)H_(3)`, ii. `overset(o-)(N)H_(2)`, iii. `overset(o-)(O)H`, iv. `F^(o-)`

Options

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

Explanation

To determine the decreasing nucleophilic order of the given compounds, we need to analyze the nature of the central atoms in each anion and their electronegativities. The compounds given are:

i. \( \overset{o-}{C}H_3 \) (methanide or carbanion)
ii. \( \overset{o-}{N}H_2 \) (amide)
iii. \( \overset{o-}{O}H \) (hydroxide)
iv. \( F^{o-} \) (fluoride)

### Step-by-Step Solution:

1. **Identify the Central Atoms**:
- The central atoms in the compounds are carbon (C), nitrogen (N), oxygen (O), and fluorine (F).

2. **Determine Electronegativity**:
- The electronegativity values for these elements (in increasing order) are:
- Carbon (C) < Nitrogen (N) < Oxygen (O) < Fluorine (F)
- This means that carbon is the least electronegative, while fluorine is the most electronegative.

3. **Understand Nucleophilicity**:
- Nucleophilicity is inversely related to electronegativity. The less electronegative the atom, the more nucleophilic it is. This is because less electronegative atoms are more willing to donate their electron pairs.

4. **Rank the Compounds Based on Nucleophilicity**:
- Since carbon is the least electronegative, \( \overset{o-}{C}H_3 \) (carbanion) will be the most nucleophilic.
- Next, \( \overset{o-}{N}H_2 \) (amide) will be more nucleophilic than \( \overset{o-}{O}H \) (hydroxide) because nitrogen is less electronegative than oxygen.
- Finally, \( F^{o-} \) (fluoride) will be the least nucleophilic due to fluorine's high electronegativity.

5. **Final Order**:
- Therefore, the decreasing nucleophilic order is:
- \( \overset{o-}{C}H_3 \) > \( \overset{o-}{N}H_2 \) > \( \overset{o-}{O}H \) > \( F^{o-} \)

### Conclusion:
The final answer for the decreasing nucleophilic order of the given compounds is:
\[ \overset{o-}{C}H_3 > \overset{o-}{N}H_2 > \overset{o-}{O}H > F^{o-} \]