## **Core Concept**
Arsenic poisoning is a significant concern in forensic toxicology, and various tests are employed to detect its presence. The tests mentioned in the options are used for detecting arsenic. Understanding the specific tests for arsenic poisoning is crucial for diagnosing and managing cases of poisoning.

## **Why the Correct Answer is Right**
The correct answer involves identifying the tests specifically used for detecting arsenic.
- **Marsh's test** is a well-known test for arsenic, involving the conversion of arsenic into arsine gas, which is then detected.
- **Reinsch's test** is another test used for arsenic, where copper foil is used to detect the presence of arsenic.
- **Macewan's test** does not directly relate to common tests for arsenic like Marsh's or Reinsch's but might be confused with tests for other substances.
- **Marqui's test** is not a commonly recognized test for arsenic in standard toxicology references.

## **Why Each Wrong Option is Incorrect**
- **Option C:** This option includes c) Macewan's test and d) Marqui's test, which are not primarily recognized for arsenic detection, making it an incorrect choice.
- **Option A and B:** These options do not include all the correct tests for arsenic poisoning.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **Marsh's test** and **Reinsch's test** are specifically used for detecting arsenic. Marsh's test is particularly notable for its sensitivity and specificity in detecting arsenic poisoning, making it a valuable tool in forensic science.

## **Correct Answer:** B. a, b.