**Explanation:**

The correct answer is option B, which involves treating coal washing wastewater in sedimentation tanks equipped with mechanical scrapers. Here is a detailed explanation of why this method is the most suitable for solid particle removal:

**Chemical Coagulation:**
- Chemical coagulation involves the addition of coagulants to wastewater to destabilize and agglomerate the suspended solids, making them easier to remove.
- While chemical coagulation can be effective for solid particle removal, it may not be the most efficient method for coal washing wastewater due to the presence of clay, slate, and stone, which can be difficult to coagulate and remove.

**Vacuum Filter:**
- Vacuum filters are used for solid-liquid separation and can be effective in removing solid particles from wastewater.
- However, vacuum filters may not be the most suitable option for coal washing wastewater due to the high concentration of suspended solids.
- The presence of clay, slate, stone, and other particles can lead to clogging and reduced filtration efficiency in vacuum filters.

**Clarifiers:**
- Clarifiers are designed to separate solid particles from wastewater through sedimentation.
- They work by allowing the suspended solids to settle at the bottom of the tank while the clarified water is collected from the top.
- Clarifiers can be effective for solid particle removal, but they may not be the most efficient option for coal washing wastewater.
- The high concentration of suspended solids in coal washing wastewater may require a longer settling time, which can reduce the overall efficiency of the clarifier.

**Sedimentation Tanks with Mechanical Scrapers:**
- Sedimentation tanks equipped with mechanical scrapers are the most suitable option for solid particle removal in coal washing wastewater.
- These tanks are designed to allow the suspended solids to settle at the bottom while the clarified water is collected from the top.
- The mechanical scrapers continuously remove the settled solids from the bottom of the tank, preventing the accumulation of sludge and maintaining the efficiency of the tank.
- The presence of clay, slate, stone, and other particles in coal washing wastewater can be effectively removed and collected by the mechanical scrapers in sedimentation tanks.
- This method ensures efficient solid particle removal and allows for the effective treatment of coal washing wastewater.