Work out each item in English

From the graph provided (Activity vs. Time), we look for the time when the isotope's activity reaches the background count rate of 50 counts per minute.
From the graph, drawing a horizontal line from 50 on the 'Activity (counts per minute)' axis to the curve, then dropping a vertical line to the 'Time (minutes)' axis, we find a time of approximately 13.25 minutes.

The parents need to wait for $\boxed{\text{13.25 minutes}}$.

Before the duration of 13.25 minutes, the radiation from the radioactive isotope is too hazardous and can cause harm to the parents. Waiting until the activity has decayed to 50 counts per minute ensures that the radiation levels have reduced to a safe level, close to the natural background radiation, thus minimizing the risk of harm.

• Parents should not eat or drink inside the isolation room.
• They should wear personal protective equipment such as gloves, boots, and lead aprons.
• They should avoid direct contact with the patient.
• They should minimize their time spent inside the room.
• If they have any wounds, they should cover them with thick cloth.

These precautions are essential because radiation can cause severe health problems, including:

• Causing cancer.
• Causing infertility.
• Causing skin burns or rashes.
• Causing genetic mutations.
• Causing blindness.