Complete the sentence with the correct words.

Before flying home, I met Dr Davis Billings, ... He told me that life-threatening complaints such as cancer, diabetes and heart disease are rare in Okinawa. It seems that Okinawans not only live longer, but they also live better.

• who has studied Okinawa’s centenarians for more than a decade.
• which the Okinawans firmly believe helps to prevent illnesses.
• which the Okinawans firmly believe helps to prevent illnesses.
• which is a healthy food and very low in calories.
• who also looked younger than her 76 years.
• that the family only ate small portions.
• since my arrival in Okinawa.