Final answer:
A liquid stool specimen for ova and parasites must be sent immediately to the laboratory and examined within 30 minutes to ensure accurate results.
Step-by-step explanation:
A liquid stool specimen for ova and parasites must be sent immediately to the laboratory and examined within 30 minutes to ensure accurate results. This is because ova (eggs) and parasites may degrade quickly in liquid stool samples, making it difficult to identify them under the microscope. The examination within 30 minutes ensures that the ova and parasites are still viable and can be properly observed and diagnosed.