What must a nursing home do in conjunction with the pharmacist or pharmacy service?

A nursing home must work closely with the pharmacist or pharmacy service in order to maintain an emergency and contingency drug supply for their patients. This option is correct because it highlights the vital role that pharmacists and pharmacy services play in the healthcare system, particularly in the context of a nursing home. Option A is incorrect because pharmaceutical training is not the main task that a nursing home must do in conjunction with the pharmacist. Option C is incorrect because nursing homes do not typically offer pharmacy services to the public, they are primarily focused on serving their residents. Option D is incorrect because nursing homes are not involved in drug trials, which are often conducted by pharmaceutical companies or research institutions.