Answer:
Thread.
Explanation:
The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside.
Answer:
The basic principle on which the electric iron works is that when a current is passed through a piece of wire, the wire heats up. This heat is distributed to the sole (base) plate of the electric iron through conduction.
That's true.
In fact, the resistance of a wire is given by:

where

is the resistivity of the material
L is the length of the wire
A is the cross-sectional area of the wire
We see that the resistance of the wire is inversely proportional to the cross-sectional area: A. Therefore, the narrower the wire, the smaller A, the larger the resistance. But higher resistance means that the current flowing through the wire is lower, therefore the flow of electrons in the circuit is slower, and the initial sentence is true.
Answer;
The Epidermis; stratum corneum layer
Explanation;
The distal end of each digit is protected by a strong plate of hard keratin, called a nail or nail plate, which grows out from a nail bed. The nail bed, is a specialized form of skin epithelium, and has the same four layers of the epidermis of skin, with the nail plate being analogous to the stratum corneum layer.
The nail plate is made up of tightly packed, hard, keratinized epidermal cells. It has a nail body, a free edge, and extends deep into the dermis at the proximal end to form the nail root.