What has led to an improvement in life expectancy?

A statistical measurement of the average time a person is expected to live is a life expectancy and it depends on many factors.

These days we see some improvement in life expectancy, this is because now medical health care has been improved. Death rates from infectious diseases have fallen and life expectancy his improved and the second thing is a healthy life style is very important for the improvement of life expectancy.

Betray, destroy, and obey do not need to be changed to add the suffix -ed, because the "y" at the end of each word is preceded by a vowel  (so  they would be spelled  "betrayed," "destroyed," and "obeyed").

but hurry is different; it has to  be spelled "hurried" because the "y" at the end of "hurry" is preceded by a consonant.