Skeletal system

The clavicle (collar bone) and the scapula form the pectoral girdle; the glenoid cavity is the depression of the scapula that articulates with the head of the humerus to form the shoulder joint.
So the clavicle and glenoid cavity belong to the pectoral girdle, not the pelvic girdle. (The pelvic girdle is made of the coxal bones and has the acetabulum.)
Humerus and ulna are bones of the fore limb, which is part of the appendicular skeleton (correct).
Malleus, incus and stapes are the three ear ossicles (correct).
The sternum and ribs, with the skull and vertebral column, form the axial skeleton (correct).
Hence the non-matching pair is clavicle and glenoid cavity – pelvic girdle.

Each half of the pelvic girdle is a coxal bone, formed by the fusion of three bones: ilium, ischium and pubis. This matching is correct.
The pyrimidines are cytosine, uracil and thymine; thiamine is vitamin $B_1$, not a nitrogenous base.
The ear ossicles are malleus, incus and stapes; the cochlea is the coiled part of the internal ear.
Actin and myosin are muscle proteins, but rhodopsin is the visual pigment of the rod cells of the retina.
Hence the correct matching is ilium, ischium, pubis – coxal bones of the pelvic girdle.

Humans have 12 pairs of ribs.
The first seven pairs are true ribs (attached directly to the sternum), and the 8th, 9th and 10th pairs are false or vertebrochondral ribs (attached to the seventh rib through hyaline cartilage).
The last 2 pairs (11th and 12th) are not connected ventrally and are called floating ribs. Two pairs means 4 floating ribs in total, so this item is correct.
The number of cervical vertebrae in humans, as in almost all mammals, is 7, not 8.
The number of amino acids found in proteins is 20, not 16.
Diabetes is generally of two types: diabetes mellitus and diabetes insipidus.
So the item with the correct total number is floating ribs in humans - 4.

Humans have 12 pairs of ribs: 7 pairs of true ribs, 3 pairs of false (vertebrochondral) ribs and 2 pairs of floating ribs.
The floating ribs are the 11th and 12th pairs, which are not attached to the sternum ventrally. So floating ribs - 2 pairs is correct.
The collar bones (clavicles) are 1 pair, not 3 pairs.
The salivary glands are 3 pairs (parotid, sub-maxillary or sub-mandibular, and sub-lingual), not 1 pair.
The cranial nerves in humans are 12 pairs, not 10 pairs.
So the anatomically correct statement is floating ribs - 2 pairs.