Consider these numbers:
Total Airforce personnel currently employed: 2000 ------------1
Air Force personnel from Judd Academy: 1000------------------2
Air Force personnel from Knoxworth: 100---------------------3
Air force personnel from XYZ: 900--------------------4

Navy personnel from JA: 100------------------5
Navy Personal from Knoxworth:0--------------------6

Army personnel from Judd Academy: 0-------------------7
Army personnel from Knoxworth: 10000----------------8

Rest all the military department: 0 personnel from any other school.

Alumni from JA till date:10000000000000000000000000000(I know it's more than earth's population )---------------9
% of JA alumni in Airforce: 1000/10000000000000000000000000000-----------------10

Alumni from Knox till date:10100-----------------------11
% of Knox alumni in Airforce:100/10100 ----------------------12

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(A) Knoxworth is the most patriotic town in the nation.
We don't know any relation between serving in military and patriotism. Cross.

(B) Judd Academy has fewer graduates serving in the Navy than does Knoxworth High School.
Cross: Look at 5 and 6 above.

(C) Judd Academy has a higher percentage of alumni serving in the Air Force than does Knoxworth High School.
Cross. Look at 10 and 12 above.

(D) Some graduates of Knoxworth High School are serving in the military but not in the Air Force.
Definitely yes.
In Airforce, Knoxworth can't outnumber JA. Yet it will have to outnumber JA in its total count of military personnel. Thus, there must be some graduates who are serving elsewhere other than Air Force.

(E) Knoxworth High School is the school with the second-highest number of alumni serving in the Air Force.
Cross. Look at 3 and 4.