Task: Question Answering
Input (English): Question: For a drug to permeate through the cornea, you must: 
 Options:  <1> Be totally ionized. <2> Present a very high polarity. <3> Join the lysozyme that is present in the tear fluid. <4> Present a certain lipophilicity and a minimum degree of water solubility. <5> Have weak acid character.
Output (English): 4