7806 wrote:A)After the Colonial period's 50 percent mortality rate, life expectancy improved for children, but as late as the nineteenth century about one child in three died before reaching the age of six.

-incorrect...why is it sentence fragment. how.?

(C) Although life expectancy for children improved unchanging after the Colonial period, during which the mortality rate was 50 percent, as late as the nineteenth century about one child in three died before reaching the age of six.

i know C is correct.... pl tell about A.).

After the Colonial period's 50 percent mortality rate, life expectancy improved for children, but as late as the nineteenth century about one child in three died before reaching the age of six.

After... introduces a dependent clause.
After Sunset, I will take my Dinner.
After Sunset is dependent clause and the clause following the comma is an independen clause.
In this case : I will take my dinner.

Similar to After is But.
But is similar to After. But "But" can also be used to link 2 independent clauses.
I want to go to the movie, But I have no time.

In option A above, both the clauses introduced by After and But are dependant clauses. They do not have the Subject and verb of their own.

Hence the sentence is a fragment.

Hope this helps!!

I request others to correct me if I am wrong.