1. Explaining these pronunciations involves two steps: first, figure out what the relevant environments are; and second, try to work out why the learner is producing these pronunciations in those environments. In terms of environments, [d] appears word-initially and word-finally, and [d] medially, between vowels; [ʃ] appears before or after an [Ι] vowel, and [s] next to other vowels. Since we know the speaker in this case is a learner of English, our first attempt at explanation might involve the patterns of her native language: we can hypothesise that in that language, [d] and [d] are allophones of a single phoneme, and likewise [ʃ] and [s] are allophones of a single phoneme, with a distribution like the one our learner imposes on English.
Predicted pronunciations would be: Daddy [dæði]; either [ð]; loathe [d]; ship [ʃ]; pass [s]; dish [ʃ]; usher [s].
2. One list of minimal pairs for initial position would be my – nigh – pie – buy – tie – die – guy – lie – rye. You can add me – key in a slightly different context. You should be able to produce similar lists medially and finally; what you won't find are cases of initial [ŋ], final [h], or for some speakers at least, final [r].
3. The main point here is that some pairs of sounds are in complementary distribution in this language: notably, voiced and voiceless pairs of sounds ([g] – [k], [b] – [p], [z] – [s]) do not contrast, since the voiced one appears initially and medially, and the voiceless one finally. Linguist A has noticed this, and uses a single symbol for each pair; Linguist B uses different graphs. Linguist A also uses a single symbol for [ŋ], which is a single consonant in this language, and represents [h] with each time it is pronounced. Linguist B uses for [ŋ], making it look like two consonants, and has no symbol for [h] word-finally. In short, A is using a system designed for this particular language; B is following English patterns, and is probably a native speaker of English.
1. (a) hang, ship, foot, sit
(b) nap, jug, knock, lot, jump
(c) nap, hang, jug, bet, lamb
(d) pot, sad, boss, size, hen, call
(e) wash, hall, red, yellow
2. (a) They are all approximant consonants
(b) They are all voiceless
(c) They are all fricatives.