Explanation

Coal can be converted to petroleum through the Fischer-Tropsch process. 

The Fischer-Tropsch process is a series of chemical reactions

That converts carbon monoxide and hydrogen (syngas) into liquid hydrocarbons, which can be used as a substitute for petroleum. 

Explanation

In butterflies, the female is XY or X0. 

Butterflies have a unique sex determination system where males have two or more X chromosomes (XX, XXX, etc.)

And females have one X chromosome and either another X or no second sex chromosome (XY or X0).

This differs from humans and most mammals, where females are XX and males are XY. 

Explanation

 The endocrine gland that secretes oxytocin is the Pituitary gland. 

While oxytocin is produced in the hypothalamus,

It is stored and released by the posterior pituitary gland. 

Explanation

In a closed organ pipe, the fundamental frequency is f = v / 4L.  

If both ends are opened, it behaves like an open pipe, and the fundamental frequency becomes f' = v / 2L.

So, f' = 2f.

Explanation

The reverse process of X-ray production is related to the "photoelectric effect". 

Photoelectric effect: In this process, a high-energy photon interacts with an atom, transferring all its energy to an electron and ejecting it from the atom.

This is the reverse of X-ray production, where electrons are accelerated to high speeds and generate X-rays when they collide with a target atom. 

Explanation

Tetrahedral geometry: This means the central carbon atom is surrounded by four atoms (three hydrogen atoms and one chlorine atom) arranged in a three-dimensional pyramid shape. 

Explanation

 The direction of energy flow in an ecosystem is unidirectional, moving through various trophic levels successively.

It begins with the input of solar energy, which is captured by primary producers, such as plants, through photosynthesis.

Explanation

Add some milk and sugar to your tea.

When adding ingredients to a liquid, "to" is the appropriate preposition.