Arrange the following in order of increasing acidic strength
(i) `HCOOH,ClCH_(2)COOH,CH_(3)COOH`
(ii) `CH_(3)COOH,(CH_(3))_(2)CHCOOH,(CH_(3))_(3)CCOOH`
(iii) `ClCH_(2)COOH,Cl_(2)CHCOOH,ClCl_(3)C.COOH`
(iv)`ClCH_(2)COOH,CH_(3)CH_(2)COOH,ClCH_(2)CH_(2)COOH,(CH_(3))_(2)CH.COOH,CH_(3)COOH.`

Explanation

To arrange the given compounds in order of increasing acidic strength, we will apply the concepts of electron-withdrawing and electron-releasing effects.

### Step-by-Step Solution:

#### (i) `HCOOH, ClCH2COOH, CH3COOH`
1. **Identify the Compounds**:
- HCOOH (Formic acid)
- ClCH2COOH (Chloroacetic acid)
...