Given a text passage, come up with an appropriate title for it. The title should accurately represent what the main focus of the passage is. The title of a passage may be present in the first few sentences of the passage and/or be referred to multiple times in the passage. The title should be 1-5 words long.
One example is below.
Q: The Beatles ' rooftop concert was the final public performance of the English rock band the Beatles . On 30 January 1969 , the band , with keyboardist Billy Preston , surprised a central London office and fashion district with an impromptu concert from the roof of the headquarters of the band 's multimedia corporation Apple Corps at 3 Savile Row . In a 42 - minute set , the Beatles were heard playing nine takes of five songs before the Metropolitan Police Service asked them to reduce the volume . Footage from the performance was later used in the 1970 documentary film Let It Be .

A: The Beatles' rooftop concert
Rationale: 'The answer given is correct because it is an appropriate title as it is the main subject of the passage.
Q: At liquid -- air interfaces , surface tension results from the greater attraction of liquid molecules to each other ( due to cohesion ) than to the molecules in the air ( due to adhesion ) . The net effect is an inward force at its surface that causes the liquid to behave as if its surface were covered with a stretched elastic membrane . Thus , the surface becomes under tension from the imbalanced forces , which is probably where the term '' surface tension '' came from . Because of the relatively high attraction of water molecules for each other through a web of hydrogen bonds , water has a higher surface tension ( 72.8 millinewtons per meter at 20 C ) compared to that of most other liquids . Surface tension is an important factor in the phenomenon of capillarity .
A:
Surface tension