In the sentence “we had fun” coded as “lak mak nak”, we see that “fun” corresponds to “nak”.
In the sentence “we have brain” coded as “mak chak sake”, “have” corresponds to “mak”.
In the sentence “have some fun” coded as “chak tek nak”, we can infer that “fun” is coded as “nak”, leaving “some” as “tek” since the other words have already been coded.
The correct code for the word “some” is (b) tek.