When /d/ is in the final position, be sure to make it audible.
Try the following with the /t/ /d/ sounds: taa, taw, toe, too, tea, tie, toy, tou(t), tay; daa, daw, doe, do, dee, die, doy, dow, day.
Also try the following pairs of words on one air intake wherever possible: top-tap, tab-tub, pot-put, pit-peat, dip-deep, dope-daub, bid-bed, pod-pad; also Tad-dad, Ted-dead, tip-dip, pat-pad, but-bud, at-add.
In pronouncing /k/ and /g/ the air passage is blocked by raising the back of the tongue to touch the soft palate, the soft palate being also raised so as to shut off the nose passage; when the contact of the tongue with the palate is released by lowering the tongue the air compressed by pressure from the esophagus suddenly escapes through the mouth, making an explosive sound.
