Condom poster: What should 爪 in ...因爪安全性行为感染艾滋病 actually be? And why is 经 in 预防艾滋病经性传播?
It is 不安全性行为 (unsafe sex) , not 爪安全性行为

经 means 'through'

性 means 'sex'

预防艾滋病(经)性传播 = prevent aids spread (through) sex

A more clear phrasing might help new learners understand better - 预防艾滋病经(由)性(愛/交)传播

经由 = 'through'

性愛 = 'love making'

性交 = 'sexual intercourse'