For the compounds
`CH_3Cl,CH_3Br,CH_3I "and" CH_3F`
the correct order of increasing C-halogen bond length is:

Options

A. `CH_3F lt CH_3Cl lt CH_3Br lt CH_3I`
B. `CH_3F lt CH_3Br lt CH_3Cl lt CH_3I`
C. `CH_3F lt CH_3I lt CH_3Br lt CH_3Cl`
D. `CH_3Cl lt CH_3Br lt CH_3F lt CH_3I`

Explanation

To determine the correct order of increasing C-halogen bond length for the compounds CH₃Cl, CH₃Br, CH₃I, and CH₃F, we need to consider the size of the halogen atoms and how that affects the bond length.

### Step-by-Step Solution:

1. **Identify the Halogens and Their Sizes**:
- The halogens involved are Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).
- The atomic sizes of these halogens increase in the order: F < Cl < Br < I.
- This means that Fluorine is the smallest atom, while Iodine is the largest.

2. **Understanding Bond Length**:
- Bond length is the distance between the nuclei of two bonded atoms.
- As the size of the halogen atom increases, the bond length between carbon and the halogen also increases.

3. **Comparing the Bond Lengths**:
- For CH₃F, the bond length will be the shortest because Fluorine is the smallest halogen.
- For CH₃Cl, the bond length will be longer than CH₃F, as Chlorine is larger than Fluorine.
- For CH₃Br, the bond length will be longer than CH₃Cl, as Bromine is larger than Chlorine.
- For CH₃I, the bond length will be the longest because Iodine is the largest halogen.

4. **Establishing the Order**:
- Therefore, the order of increasing C-halogen bond length is:
- CH₃F < CH₃Cl < CH₃Br < CH₃I

5. **Final Answer**:
- The correct order of increasing C-halogen bond length is: **CH₃F < CH₃Cl < CH₃Br < CH₃I**.