在於

to be in / to lie in / to consist in / to depend on / to rest with

to exist; to be alive / (of sb or sth) to be (located) at / (used before a verb to indicate an action in progress)

surname Yu / Taiwan pr. [Yu2]

(literary) Oh! / Ah!

(of time or place) in; at; on / (indicating any indirect relation) to; toward; vis-à-vis; with regard to; for / (indicating a source) from; out of / (used in comparison) than / (used in the passive voice) by

the problem is...

the whole year must be planned for in the spring (idiom) / early planning is the key to success

make your day's plan early in the morning (idiom) / early morning is the golden time of the day

life is motion (popular saying with many possible interpretations) / Physical effort is vital for our bodies to function (Aristotle). / Life derives from physical exercise.