Answer:
The most obvious and widely publicized barrier to renewable energy is cost—specifically, capital costs, or the upfront expense of building and installing solar and wind farms. Like most renewables, solar and wind are exceedingly cheap to operate—their “fuel” is free, and maintenance is minimal—so the bulk of the expense comes from building the technology.
The external ear structure is called the Pinna.
The Pinna helps to channel sound waves into the ear.
Many animals have the ability to move their pinna towards the direction of sound.
I have attached an image of a dog's ear to show you the external structure called the Pinna.
I hope this helps! I'm happy to answer any other questions you might have :)
[Image sourced from: https://www.msdvetmanual.com/dog-owners/ear-disorders-of-dogs/ear-structure-and-function-in-dogs]
Answer:
Fertilizers replace the nutrients that crops remove from the soil. Without the addition of fertilizers, crop yields and agricultural productivity would be significantly reduced. That's why mineral fertilizers are used to supplement the soil's nutrient stocks with minerals that can be quickly absorbed and used by crops