Answer:
A recent study shows that about 43% of medical doctors have a solo practice with a margin of error of 4.6 percentage points.
Explanation:
Given that a random sample of 311 medical doctors showed that 135 had a solo practice.
Sample proportion = 0.43
Std error of sample proportion =

Margin of error 90%

Margin of error in percent = 4.6%
Hence correction option is:
A recent study shows that about 43% of medical doctors have a solo practice with a margin of error of 4.6 percentage points.