Select the most appropriate option to fill in the blank.
When my mother was going to the market she_______to a old friend who used to study with her in the same school.
a) Go across
b) Went across
c) Come across
d) Came across
‘come across’ is a prepositional phrase which means ‘to meet by chance’ and the given sentence is in past tense so we need to use past form of the verb come, that is option d ‘came across’.