Whats the meaning of until and so that?

[Utra]

English Language Tests, Intermediate level

ESL/EFL Test #171 "Common subordinating conjunctions", question 7

Elena will groom the horse in the morning ......... she can ride it in the afternoon.

(a) until
(b) unless
(c) so that
(d) when

English Language Tests, Intermediate level

ESL/EFL Test #171 "Common subordinating conjunctions", answer 7

Elena will groom the horse in the morning so that she can ride it in the afternoon.

Correct answer: (c) so that
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what´s the meaning of until and so that?

[Mister Micawber]

Until:
–conjunction
1. up to the time that or when; till: He read until his guests arrived.
2. before (usually used in negative constructions): They did not come until the meeting was half over.
–preposition
3. onward to or till (a specified time or occurrence): She worked until 6 p.m.
4. before (usually used in negative constructions): He did not go until night.
5. Scot. and North England. to; unto.

So that:
–conjunction
18. in order that : Check carefully, so any mistakes will be caught.
19. with the result that : He checked carefully, so that the mistakes were caught.
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Native English teacher at Mister Micawber's