Fill in the blank by choosing the appropriate word/words from those given in the brackets.
(acetaldehyde, formaldehyde, benzaldehyde, yellow, white, violet, Cannizzaro's, Liebermann, no `alpha`-hydrogen atom, `1alpha`-hydrogen atom, `2alpha`-hydrogen atoms, aldol, `beta`-hydroxy aldehyde, aldol condensation, mixed condensation, + I,-I, -M,+ M. decreases, increases, benzalchloride, PCI, SOCh. sec, alcohol, tert, alcohol, phenylhydrozone, semicarbazone, more, less, acetals, ketals, silver mirror, test, urotropine, acetaldehyde cyanohydrin, lactic acid, benzoic acid, Sodalime, ethanoic acid, propanoic acid, electrolysis, Kolbe's electrolytic reaction, carbon dioxide, water, amides, alpha, halogen, phosphorus, weaker, stronger, ethyl alcohol, dibasic,monobasic, 2,2-dimethylpropanoic acid, `CH_(3)COCI`, acetic acid, `CH_(3)CH_(2)CH_(2)COOK`, enatiomers, diastereo, `K_(a)` `pk_(a)`, methanoic acid, higher, lower.)
The meso and (+)forms of tartaric acids are ............... isomers.

Explanation

To solve the question, we need to fill in the blank regarding the relationship between the meso and (+) forms of tartaric acid. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Structure of Tartaric Acid
Tartaric acid is a dihydroxy dicarboxylic acid with two chiral centers. The presence of these chiral centers means that tartaric acid can exist in different stereoisomeric forms.

### Step 2: Identify the Types of Isomers
- **Meso Compound**: A meso compound has multiple chiral centers but is superimposable on its mirror image due to an internal plane of symmetry.
- **Optically Active Isomer**: The (+) form of tartaric acid is optically active, meaning it can rotate plane-polarized light.
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