1. Your friend is messing around on the IPA keyboard, typing in random symbols and asking you to say them. He types in [ z'] and challenges you to pronounce it. You say you can't, and no one can. What would the articulatory description for this sound be, and why is it articulatorily impossible?

2. Most languages that have five distinct vowels, like Japanese, Spanish, and Hawai'ian use [i,e,a,o,u]. Why is that a better vowel inventory than, say, [i,y,i,u,u]?

3 A lot of languages with small inventories, like those in the previous question, have an odd number of vowels. There are two close vowels, two close-mid vowels, but then only one open vowel. For three-vowel systems, there's usually two close and one open. Articulatorily speaking, why does it make sense for these languages to have contrastive vowels in the close and mid heights, but not in the open height?

4. I recorded a Thai alveolar stop with a VOT of 100ms. Remember that Thai has a three- way voicing distinction, with voiced, voiceless aspirated, and voiceless unaspirated consonants. What is the best broad transcription of this sound in IPA for Thai? What would the best broad transcription be if it were a sound in American English instead? Why aren't these the same?