Hint: Insects are invertebrates which are a large group of arthropods and constitute a chitinous exoskeleton and three-part body which includes head, thorax, and abdomen. They have three pairs of jointed legs with compound eyes and one pair of antennae.
Palpigers are structures present on an insect’s labium. The labium is an insect's lower lip that is positioned towards the back of the head and helps the insect withhold food in place when the insect feeds. It represents the fused pair of ancestral second maxillae and consists of three segmented palps which are sensory. It is quadrilateral in structure and is the major component of the floor of the mouth. It assists the manipulation of food during mastication and is adapted to function especially in some insects. They fold the labium neatly beneath the head and thorax. The insect flick it out to snatch the prey and bear it back towards the head where the chewing mouthparts demolish it and swallow the remaining particles. It is attached to the ciborium which is the rear end of the structure. The labium is a long gated to form a tube and tongue in the honeybee and helps them in both chewing and lapping whereas in the wild silk moth it has small labial palps and no maxillary palpi.
Labrum: It is a flap-like structure which is located in front of the mouth and amounts to the upper lip of an insect mouth. It helps in revolutionary origin, morphological development, and embryogenesis. It helps in the development of embryonic primordium which appears at the anterior of the head which is migrated towards its adult position.
Antennae: They are the feelers and are paired appendages that are used for sensing and are connected to the two segments of the arthropod head. They are modified for mating, brooding, swimming, and anchoring in some arthropods. They can locate other group members like an ant.
Maxillae: It is located beneath the mandibles and is paired with maxillae to manipulate in chewing insects and partly masticate the food. It consists of the proximal cardo and the distal stripes. The distance types consist of the inner lacinia and the outer galea which is cupped or scoop-like in structure and is located over the outer edge of the labium. The maxillae help in the functioning of the mandibles in feeding and are motile and less heavily sclerotized. They manipulate the soft, liquid, or particulate food besides cutting or crushing food.
So, the correct answer is 'Labium'.
Note: Insects are known for about 6 to 10 million in species and have two antennae with three pairs of legs. Some insects like Gerridae are capable of walking on the surface of the water. Insects do not breathe using their mouths but breathe through the holes present in their exoskeletons known as the spiracles.