Final answer:
The /ch/ sound spelled as -tch follows a stressed short vowel in English words. Other patterns depend on whether consonants follow the stressed vowel, which can alter the spelling of sounds like /k/ and /t/.
Step-by-step explanation:
The combination -tch for the /ch/ sound in English spelling typically follows a stressed short vowel.
For example, in words like 'catch' and 'pitch', the sound /ch/ comes at the end of a free stem and after a stressed short vowel, leading to the use of -tch. When there is a vowel in front of the /ch/ that is stressed, it is usually a short vowel.
However, if there is a consonant between the short vowel and the /t/, as in 'gentle' and 'mantle', a single t is sufficient, forming the VCCle pattern. When no other consonant is present, as in 'bottle' and 'little', it necessitates using both ts.
When the /k/ sound is involved in front of le at the end of a word, the spelling varies depending on the stress and length of the preceding vowel.
For a short stressed vowel, /k/ is spelled 'ck', as in 'tackle', whereas for a long stressed vowel, it can be a simple 'c' or 'k', depending on whether the sound follows a consonant or vowel respectively, as seen in 'ankle' and 'article'.