to look at (a person, thing) carefully in order to learn something; to put questions to (a person) in order to test knowledge or get information

analyse, test

to travel into or through (a country etc) for the purpose of learning about it

investigate; survey

to go to or near (a place or area occupied by enemy forces) to learn about their position, strength etc

investigate; survey

to put (something), separate (something) by putting, through a sieve; to examine something carefully

take out residue; remove impurities