A、A machine. B、Wires. C、A soft hat. D、Helmet. D录音中说“In this treatment，patients wear a helmet—a large hard hat on their head”，即需要

People suffering from depression are finding help when electromagnetic waves enter their brains.
    Mental health experts estimate that depression affects more than 120 million people worldwide. It severely affects the person’s quality of life and, in extreme cases, can lead to suicide.
    Anti-depressant medicines have been shown as an effective treatment for many patients. But the drugs are unable to help some people with the disorder.
    For such persons, doctors may suggest deep transcranial magnetic stimulation or DTMS for short.
    In this treatment, patients wear a helmet — a large hard hat on their head. The helmet is connected to a machine.
    An electric coil in the helmet sends out regular pulses of electromagnetic energy. These beating sounds produce changes in the brain area responsible for the disorder.
    Electromagnetic brain stimulation is not new. It was first used to treat depression over 30 years ago. Now, a new generation of wiring can direct the energy to one part of the brain. DTMS starts with daily 20-minute-long treatments for 20 to 30 days. The patient then returns for treatment two to three times a week for several weeks.
    The only side effect is sometimes minor head pain.
    Questions 26-30 are based on the passage you have just heard:
    26. How many people in the world are suffering from depression?
    27. What is true about anti-depressant medicines?
    28. What should a depression patient wear in the DTM treatment?
    29. Is the treatment a new invention?
    30. What is the side effect of the new way?