The correct statement(s) is /are

Options

A. Thermal stability of alkaline earth metal chloride decrease with increasing molecular mass but reverse order is true for their melting point.
B. Thermal stability of boron halides increase with decreasing molecular mass but reverse order is true for their melting point
C. Thermal stability of beryllium halides increase with decreasing molecular mass and same order is also true for their melting point
D. Thermal stability of hydra acids of halogens increase with decreasing molecular mass and same order is also true for their melting point

Explanation

To solve the question regarding the correct statements about the thermal stability and melting points of alkaline earth metal halides and boron halides, we will analyze each statement step by step.

### Step 1: Analyze the First Statement
The first statement claims that the thermal stability of alkaline earth metal chlorides decreases with increasing molecular mass, while the reverse order is true for their melting point.

**Analysis:**
- Alkaline earth metal chlorides (e.g., BeCl2, MgCl2, CaCl2, etc.) do exhibit a trend where thermal stability generally increases with increasing molecular mass, contrary to what the statement suggests.
- For melting points, the trend is also not straightforward and does not follow the reverse order as stated.

**Conclusion:** The first statement is **incorrect**.

### Step 2: Analyze the Second Statement
The second statement claims that the thermal stability of boron halides increases with decreasing molecular mass, while the reverse order is true for their melting point.

**Analysis:**
- Boron halides (e.g., BF3, BCl3, BBr3, BI3) do show that as the molecular mass decreases, the thermal stability increases.
- The melting points of boron halides also show that as the molecular mass increases, the melting points decrease, which aligns with the statement.

**Conclusion:** The second statement is **correct**.

### Step 3: Analyze the Third Statement
The third statement claims that the thermal stability of beryllium halides increases with decreasing molecular mass, and the same order is true for their melting point.

**Analysis:**
- Beryllium halides (e.g., BeF2, BeCl2, BeBr2, BeI2) show that thermal stability does not consistently increase with decreasing molecular mass; rather, it is influenced by the nature of the halide.
- The melting points also do not follow the same trend as suggested in the statement.

**Conclusion:** The third statement is **incorrect**.

### Final Conclusion
Based on the analysis:
- The correct statements are: **Only the second statement is correct.**