The decreasing basic order of the following 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 basic order of the given anions, we need to analyze the central atoms of each anion and their electronegativities. The anions provided are:

1. \( \overset{o-}{C}H_3 \) (methanide)
2. \( \overset{o-}{N}H_2 \) (amidide)
3. \( \overset{o-}{O}H \) (hydroxide)
4. \( F^{o-} \) (fluoride)

### Step 1: Identify the central atoms and their electronegativities
The central atoms in the anions are carbon (C), nitrogen (N), oxygen (O), and fluorine (F). The electronegativities of these elements (on the Pauling scale) are approximately:
- Carbon (C): 2.5
- Nitrogen (N): 3.0
- Oxygen (O): 3.5
- Fluorine (F): 4.0

### Step 2: Understand the relationship between electronegativity and basicity
Basicity is inversely related to the electronegativity of the central atom. This means that the less electronegative the central atom, the stronger the base (or the more basic the anion). Therefore, we can establish the following order based on electronegativity:

- Carbon (C) is the least electronegative, hence it will be the most basic.
- Nitrogen (N) is next, so it will be less basic than carbon but more basic than oxygen and fluorine.
- Oxygen (O) is more electronegative than nitrogen, making it less basic.
- Fluorine (F) is the most electronegative, thus it will be the least basic.

### Step 3: Write the decreasing order of basicity
Based on the analysis of electronegativities, we can write the decreasing order of basicity for the given anions as follows:

1. \( \overset{o-}{C}H_3 \) (most basic)
2. \( \overset{o-}{N}H_2 \)
3. \( \overset{o-}{O}H \)
4. \( F^{o-} \) (least basic)

### Final Answer
The decreasing basic order of the given anions is:
\[ \overset{o-}{C}H_3 > \overset{o-}{N}H_2 > \overset{o-}{O}H > F^{o-} \]