At a four-legged table there is 1 grandpa, 2 dads, 2 sons and a grandson. How many legs are under the table?

6 legs

Explanation:

1 grandpa: the grandpa is the father (dad number 1) of one of those seated.

Son number 1: The grandpa has a son.

Son number 2: The grandpa's son also has a son.

This makes him a dad (Dad number 2).

The son of the grandpa's child is the grandpa's grandson.

We can say from the above, a man (grandpa) has a Son and a grandson.

Each person has two legs.

For 3 persons, we would have = 2×3 = 6legs

Therefore a 4 legged table with 1 grandpa, 2 dads, 2 sons and a grandson have 6 legs under the table.

Explanation:

This one is definitely incorrect.

If attendees have questions, she should stop at the information counter.

Attendees means more than 1. She is (especially in this case) singular (meaning one).

If an attendee has questions, she should stop at the information counter.

or

If attendees have questions, they should stop at the information counter.