One feature of a less developed nation is

Question

high infant mortality rates
high levels of modernization
high levels of industrialization
high per capita income

not sure

Answer 1

Look up all of the unfamiliar terms. The answer is obvious.

Answer 2

Now, now! You're smart, you can figure out that "less developed" means less of things that "more developed" nations might have, like industry, modern amenities (water and sewage treatment, internet, telephones, etc.) and high incomes. But with less of some things we think of as essential the infant mortality rate is high, as in less medical sophistication.

Answer 3

high infant mortality rates