Final answer:
Option (1), The best adaptation is 'know yourself', reflecting themes of self-awareness and authenticity echoed in both Western and Eastern philosophical texts.
Step-by-step explanation:
The best adaptation of the underlined part of the excerpt 'To thine own self be true' from Hamlet would be know yourself. This adaptation aligns with the message of self-awareness and authenticity presented in various philosophical and literary sources. For instance, Socrates emphasizes the importance of self-examination and knowing one's own nature and limits, which is encapsulated in the maxim from the temple at Delphi: 'know thyself'.
Additionally, various sayings and proverbs from Eastern philosophy, such as 'The essence of knowledge is, having it, to use it' and 'To know what you know and what you do not know, that is true knowledge', also echo the theme of self-knowledge as pivotal to leading a purposeful and truthful life.