The gold numbers of protective colloids A, B, C and D are 0.04, 0.004, 20 and 30 respectively.
The protective powers of A, B, c and D are in order

Options

A. `BgtAgtCgtD`
B. `AgtBgtCgtD`
C. `DgtAgtBgtC`
D. `BgtCgtDgtA`

Explanation

To determine the order of protective powers of the protective colloids A, B, C, and D based on their gold numbers, we can follow these steps:

### Step 1: Understand Gold Numbers
Gold numbers indicate the minimum amount of protective colloid required to prevent coagulation of a standard gold sol. A lower gold number means that less colloid is needed to achieve the same protective effect, indicating a higher protective power.

### Step 2: List the Gold Numbers
The gold numbers for the protective colloids are as follows:
- A: 0.04
- B: 0.004
- C: 20
- D: 30

### Step 3: Determine the Inverse Relationship
Since the protective power is inversely proportional to the gold number:
- Lower gold number → Higher protective power
- Higher gold number → Lower protective power

### Step 4: Rank the Protective Powers
Now, we can rank the protective powers based on the gold numbers:
1. B (0.004) - Highest protective power
2. A (0.04) - Second highest protective power
3. C (20) - Third highest protective power
4. D (30) - Lowest protective power

### Step 5: Write the Order of Protective Powers
The order of protective powers from highest to lowest is:
- B > A > C > D

### Final Answer
The protective powers of A, B, C, and D are in the order: **B > A > C > D**.

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