TASK DEFINITION: In this task, you are given a sentence and question which can be answered using the sentence. Your task is to answer the question using the information from the sentence. The answer to the question is unique and it is a continuous text span from the sentence.
PROBLEM: Sentence: A nonsurgical alternative involves the use of a miotic to constrict the pupil and prevent the lens from luxating into the anterior chamber . 
 Question: what is  prevented?

SOLUTION: the lens from luxating into the anterior chamber

PROBLEM: Sentence: Instead , much of numerical analysis is concerned with obtaining approximate solutions while maintaining reasonable bounds on errors . 
 Question: what might something obtain?

SOLUTION: approximate solutions

PROBLEM: Sentence: When BrdU is integrated into DNA , it is supposed that the bromine deforms the minor groove so that Hoechst dyes can not reach their optimal binding site . 
 Question: what ca n't something reach?

SOLUTION:
their optimal binding site