Decreasing `-I` effect of given is:
(i) `CN` , (ii) `NO_(2)`
(iii) `NH_(2)` , (iv) `F`

Options

A. `iiigtiigtigtiv`
B. `iigtiiigtivgti`
C. `iiigtiigtivgti`
D. `iigtigtivgtiii`

Explanation

To determine the decreasing -I (negative inductive) effect of the given groups (CN, NO2, NH2, and F), we can follow these steps:

### Step 1: Understand the -I Effect
The -I effect refers to the electron-withdrawing ability of substituents. Groups that have a strong -I effect pull electron density away from the rest of the molecule, leading to a partial positive charge on the adjacent carbon atoms.

### Step 2: Identify the Groups
The groups provided are:
1. CN (Cyano group)
2. NO2 (Nitro group)
3. NH2 (Amino group)
4. F (Fluorine)

### Step 3: Analyze Each Group's -I Effect
- **CN (Cyano group)**: This group has a strong -I effect due to the electronegativity of nitrogen and the triple bond with carbon, making it a strong electron-withdrawing group.
- **NO2 (Nitro group)**: This group is also a very strong -I group because of the presence of multiple electronegative oxygen atoms and resonance structures that stabilize the electron-withdrawing effect.
- **F (Fluorine)**: Although fluorine is highly electronegative, it has a weaker -I effect compared to CN and NO2 because it can also exhibit a +I effect due to its lone pairs.
- **NH2 (Amino group)**: This group has a +I effect due to the presence of a lone pair of electrons on nitrogen, which can donate electron density. Therefore, it has the least -I effect among the groups listed.

### Step 4: Arrange the Groups in Decreasing Order of -I Effect
Based on the analysis:
1. NO2 (strongest -I effect)
2. CN
3. F
4. NH2 (weakest -I effect)

Thus, the decreasing order of -I effect is:
**NO2 > CN > F > NH2**

### Final Answer
The decreasing -I effect of the given groups is:
**NO2 > CN > F > NH2**

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