Answer the questions in one word with help of clues and images given
Since you have apparently tried to answer the question here is my interpretation. I list the six pictures (numbered from top to bottom) and link four of them to an answer.

1 - yeast cells?

2 -  ash tree section (c)

3 - rotifer (b)

4 - muscle fibre??

5 - bacteria? (a)

6 - Leeuwenhoek's microscope (d)

According to the WP page on van Leeuwenhoek he did describe the banded pattern in muscle, but there is no mention of yeast (although he would have had no trouble seeing these cells if he could see bacteria). 

It's a very odd question.