The correct answer is option 4, lead. Chocolates can be bad for health because they may contain high levels of lead. Lead is a toxic metal that can have harmful effects on the body when ingested. It can accumulate in the body over time and cause various health problems, especially in children and pregnant women.

Options 1, 2, and 3 (cobalt, nickel, and zinc) are not typically found in high concentrations in chocolates and are not commonly associated with negative health effects when consumed in moderate amounts. However, it`s worth noting that excessive intake of any mineral or metal can potentially be harmful. Therefore, it`s important to consume chocolates and any other food in moderation to maintain a balanced and healthy diet.