Exercise 1: Focal length

To be honest, I was a bit confused by the first exercise... I had to take three pictures: one at longest focal distance, the second at the shortest focal distance and the third at a standard focal distance. I did not have any problems with first two pictures. But I struggled with understanding, what means standard focal distance. After consulting with mu tutor I got the following shots:

The picture at 'standard' focal length was at 60mm:

Here are also the two other pictures:

At the smallest focal length of 18mm:

 And at the longest focal length of 250mm: