The decreaing basic order of the following is:
i. `overset(o-)(C)N`, ii. `overset(o-)(O)H`, iii. `overset(o-)(O) Me`, iv. `overset(o-)(C)H_(3)`, v. `H^(o-)`

Options

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

Explanation

To determine the decreasing basic order of the given species, we will analyze each species and its conjugate acid. The basic strength of a species is inversely related to the acidity of its conjugate acid. Thus, we will follow these steps:

### Step 1: Identify the Species
The species given are:
1. \( \overset{o-}{C}N \) (Cyanide ion)
2. \( \overset{o-}{O}H \) (Hydroxide ion)
3. \( \overset{o-}{O}Me \) (Methoxide ion)
4. \( \overset{o-}{C}H_3 \) (Methyl anion)
5. \( H^{o-} \) (Hydride ion)

### Step 2: Determine the Conjugate Acids
To find the basic strength, we need to determine the conjugate acids of each species:
1. For \( \overset{o-}{C}N \): Conjugate acid is HCN (Hydrogen cyanide)
2. For \( \overset{o-}{O}H \): Conjugate acid is H2O (Water)
3. For \( \overset{o-}{O}Me \): Conjugate acid is CH3OH (Methanol)
4. For \( \overset{o-}{C}H_3 \): Conjugate acid is CH4 (Methane)
5. For \( H^{o-} \): Conjugate acid is H2 (Hydrogen gas)

### Step 3: Assess the Acidity of the Conjugate Acids
Now, we will assess the acidity of these conjugate acids:
1. HCN is a weak acid.
2. H2O is a neutral molecule.
3. CH3OH is a weak acid.
4. CH4 is a very weak acid (almost neutral).
5. H2 is a weak acid.

### Step 4: Rank the Acids from Strongest to Weakest
Based on the acidity:
1. HCN (strongest acid)
2. CH3OH (more acidic than water)
3. H2O (neutral)
4. H2 (weak acid)
5. CH4 (least acidic)

### Step 5: Determine the Basic Strength Order
The basic strength order of the original species will be the opposite of the acidity order of their conjugate acids:
1. \( \overset{o-}{C}H_3 \) (most basic, from CH4)
2. \( H^{o-} \) (from H2)
3. \( \overset{o-}{O}H \) (from H2O)
4. \( \overset{o-}{O}Me \) (from CH3OH)
5. \( \overset{o-}{C}N \) (least basic, from HCN)

### Final Order
Thus, the decreasing basic order of the species is:
\[ \overset{o-}{C}H_3 > H^{o-} > \overset{o-}{O}H > \overset{o-}{O}Me > \overset{o-}{C}N \]