1. A. collection /kəˈlekʃən/ B. helper /ˈhɛlpər/ C. contest /ˈkɒntɛst/ D. everyone /ˈɛvrɪwʌn/

The different sound is in option B. The underlined "h" sound in "helper" is aspirated (pronounced with a puff of air), while the other options have a voiceless /k/ sound.

2. A. father /ˈfɑːðər/ B. family /ˈfæməli/ C. happen /ˈhæpən/ D. matter /ˈmætər/

The different sound is in option C. The underlined "h" sound in "happen" is aspirated, while the other options have a voiceless /f/ sound.

3. A. standard /ˈstændərd/ B. natural /ˈnætʃərəl/ C. potato /pəˈteɪtəʊ/ D. factor /ˈfaktər/

The different sound is in option C. The underlined "t" sound in "potato" is a voiceless dental stop, while the other options have a voiceless alveolar stop /t/.

4. A. laugh /lɑːf/ B. naughty /ˈnɔːti/ C. daughter /ˈdɔːtər/ D. taught /tɔːt/

The different sound is in option D. The underlined "t" sound in "taught" is a voiceless dental fricative, while the other options have a voiceless alveolar stop /t/.

5. A. elegant /ˈɛləɡənt/ B. email /ˈiːmeɪl/ C. special /ˈspeʃəl/ D. network /ˈnɛtwɜːrk/

The different sound is in option B. The underlined "e" sound in "email" is a long vowel, while the other options have a short vowel sound.