Question 18

bromine is the only halogen and nonmetal that is normally a

a)gas

b)liquid

c)semiconductor

d)solid

Bromine is the only halogen and non-metal that is normally a liquid.

Explanation

Bromine with chemical equation has a rare property of being liquid at room temperature. It is a corrosive substance that causes horrendous burns. Also, it is considered very harmful to the atmosphere because of its destructive properties.  

It is corrosive to the human body and has the potential to damage organs. Moreover, it is dangerous for the environment, too, and excess use may deplete the ozone layer. This neat liquid should be handled with care and respect.  

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !

correct answer: understand the different control methods available

integrated pest management is an strategy that is based on the ecosystem and try to prevent the pest and the damage caused by them by applying combination of technique like habitat manipulation, biological control and use of resistant varieties.

the main aim of the integrated pest management is not to completely eliminate the pest but to strengthen the ecosystem so that conditions are favorable for plants and unfavorable for pests.