With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: Techniques like hand washing, wearing gowns, and wearing face masks can help infections pass from one person to another. Aseptic technique was introduced in medicine and surgery in the late 19th century and greatly reduced the incidence of infections caused by surgery. Frequent hand washing remains the most important defense against the spread of unwanted organisms. There are other forms of prevention such as avoiding the use of illicit drugs, using a condom, wearing gloves, and having a healthy lifestyle with a balanced diet and regular exercise. Cooking foods well and avoiding foods that have been left outside for a long time is also important.
text_B: If person 1 infects person 2, is it likely person 1 washed their hands?
YES.