Okay, let's tackle this question. The user is asking about a substance used by washermen to put marks on clothes. First, I need to figure out the core concept here. It's probably related to a common practice in laundry or textile work. Washermen often use substances that can leave visible marks, maybe for identification or to separate clothes.

So, the correct answer is likely something that's used as a marking agent. I remember that in some regions, people use a substance called 'saf' or 'saffron' for marking. Alternatively, maybe something like a dye or a specific chemical. Another possibility is a type of natural indicator. For example, turmeric could be used as it leaves a yellow stain. But I need to confirm if that's common.

Looking at the options, if one of them is turmeric, that might be the answer. Turmeric is a natural dye and leaves a distinct mark. Washermen might use it to mark clothes they handle. Other options might be unrelated substances like salt, vinegar, or baking soda, which don't leave visible marks. The key here is the substance's ability to create a visible, identifiable mark without damaging the fabric. Turmeric fits this because it's a mild dye and easily available. So the correct answer would be the option with turmeric. The other options are incorrect because they don't serve the purpose of marking. The clinical pearl here is to remember that natural dyes like turmeric are used for such purposes due to their staining properties.

**Core Concept**
This question tests knowledge of traditional substances used in laundry practices for marking textiles. Washermen (laundry workers) historically use natural dyes or stains to label clothes for identification, leveraging materials with visible, non-damaging properties.

**Why the Correct Answer is Right**
Turmeric (Curcuma longa) is a natural dye containing curcumin, which imparts a bright yellow-orange color. It is commonly used by washermen to mark clothes due to its affordability, non-toxicity, and ability to leave a distinct, wash-resistant stain. The color remains visible even after multiple rinses, aiding in sorting and identification without damaging fabrics.

**Why Each Wrong Option is Incorrect**
**Option A:** Salt is a desiccant and preservative but does not stain or mark textiles.
**Option B:** Vinegar is a mild acid used for fabric softening or removing stains, not for marking.
**Option C:** Baking soda (sodium bicarbonate) is a cleaning agent but lacks staining properties.

**Clinical Pearl / High-Yield Fact**
Remember that turmeric’s curcumin is both a dietary pigment and a traditional textile marker. Its use in laundry practices highlights its dual utility in non-clinical contexts. Avoid confusing it with synthetic dyes, which may cause allergic reactions.

**Correct Answer: C. Turmeric**

✓ Correct Answer: C. Semecarpus anacardium