Teacher:Given a disfluent sentence, modify the sentence to it to its equivalent fluent form, preserving the meaning of the sentence.
Teacher: Now, understand the problem? Solve this instance: Which is more costly,  formal, or informal imperialism or er what subtle tool can not be used in an informal imperialistic situation to expand a controlled area?
Student:
What subtle tool can not be used in an informal imperialistic situation to expand a controlled area?