A、21 years old. B、5 years old. C、17 months old. D、5 months old. C新闻中提到17个月大的双胞胎姐妹终于回到危地马拉过上新生活，由此可知C项正确。

[2]Twins born joined at the head have gone home to Guatemala five months after they were separated by medical experts in the US. Doctors are optimistic that the baby girls will now lead normal lives. [1]The 17-month-old twin girls finally went home to a new life in Guatemala after spending the last five months in a Los Angeles hospital. [2]The twins Maria Teresa Quiej Alvarez and Maria de Jesus had been born joined at the head. Their problem captured the attention of a children’s charity, which organized their trip to the US. The twin’s 21-year-old father, a banana packer, expressed his heartfelt thanks to the doctors and staff who had donated their services to perform the complex 23-hour operation. Charities and public donations took care of the two million US dollar bill. Staff who looked after the twins during their stay were sad to see them leave.
1. How old are the twin girls?
2. What is the problem of the twins?