9/10. The one I got wrong was the result of reading too quickly. My work involves a lot of writing, and I use semi-colons regularly.
The quiz highlighted a connected pet hate of mine, namely the use of "however" after a comma before another clause. For example, "She hated school, however she liked art lessons". In that situation it seems to me "but" is almost always more appropriate, and "however" should normally come at the beginning or end of sentences, or after semi-colons. For example:
She hated school. However, she liked art.
She hated school; however, she liked art.
However well-behaved the children were, the teacher was exhausted.
She hated school. Fridays were enjoyable, however.