Why do you keep on [trakassera] your brother like that?

Hint: The -ing form is required after "keep on".

harassing

In any society, there is a steady pressure to [anpassa sig] .

conform

Info: "Adjust to" has the same meaning, but needs an object.

Although he was [analfabet] , he was determined to learn to read.

illiterate

Info: "An illiterate" (as a noun) is also possible.

At least his plan is [genomförbart] .

viable realizable doable feasible

Info: Of the various answers, 'doable' is rather informal.

She was sent to speak to the [rektor] .

headmaster headmistress head principal

Info: "Principal" is for AmE.

Numerous ships were lost when they struck on the Great Barrier [rev] .

Hint: The entire name should be capitalized.

Reef reef