4. A

Math, Chinese, English, Chemistry, the failure rates of these 4 subjects are: $1\%, 2\%, 4\%, 8\%$; the sum is $15\%$. Moreover, for those who fail at least two subjects, among the above 4 subjects, at least one subject is failed, which is no less than $15\%$, so the number of people who pass at least 4 subjects is no less than $85\%$. Furthermore, it is assumed that for those who fail at least two subjects, the combination of failures reaches the minimum value. Since $1-84\%=16\%>15\%$.
4. A prestigious school has the following pass rates in a college entrance examination simulation:

Math: $99 \%$
Chinese: $98 \%$
English: $96 \%$

Chemistry: $92 \%$
Comprehensive: $84 \%$

Then the minimum possible value for the number of people who pass at least 4 subjects is ( ).
A. $85 \%$
B. $84.5 \%$
C. $86 \%$
D. $86.5 \%$