**Core Concept**
Chlorination of water is a widely practiced method for disinfecting drinking water, which involves the addition of chlorine or its compounds to kill bacteria, viruses, and other microorganisms. This process relies on the oxidation properties of chlorine to inactivate pathogens and remove organic matter.

**Why the Correct Answer is Right**
Chlorination of water is effective against a broad spectrum of microorganisms due to the formation of hypochlorous acid (HOCl) and hypochlorite ions (OCl-). These reactive species target the cell membranes of microorganisms, disrupting their structure and function. The process is also influenced by factors such as pH, temperature, and the presence of organic matter.

**Why Each Wrong Option is Incorrect**
**Option A:** Chlorine is added to water in the form of sodium hypochlorite (NaOCl) or calcium hypochlorite (Ca(ClO)2). This is a correct statement as sodium hypochlorite is commonly used in water treatment plants.

**Option B:** The chlorination byproduct, trihalomethane (THM), is a known carcinogen. This statement is incorrect as THMs are indeed potential carcinogens, but the formation of THMs is a secondary effect of chlorination, not a primary goal.

**Option C:** Chlorination of water is not effective against Cryptosporidium parvum. This statement is incorrect as chlorination is not effective against Cryptosporidium oocysts, which require alternative disinfection methods such as ozone or UV treatment.

**Option D:** The ideal pH for chlorination of water is between 7 and 8. This statement is incorrect as the ideal pH for chlorination is actually between 6.5 and 7.5, as higher pH values can reduce the effectiveness of chlorine.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the effectiveness of chlorination can be affected by factors such as pH, temperature, and the presence of organic matter, which can lead to the formation of disinfection byproducts like THMs. Regular monitoring and adjustment of chlorination levels are crucial to ensure safe drinking water.

**Correct Answer:** D. The ideal pH for chlorination of water is between 7 and 8.