The correct answer is "I can't believe he has <em>swum </em>to the island." Swum is the past principle of "swim." However, if you drop the word <em>has </em>the answer would be D and the sentence would appear much more grammatically appealing. :)
is this a question from ur school?. if so this is something you should answer or ur own......
<em>The answer to this question is D) A track system was temporarily placed on the floor.</em>
<em>Hopes this helps :)</em>
For me:
So for us to be healthy and free from silent killers we must eat the right kind and amount of food specially fruits and green leafy vegetables.