There are many kinds of compounds formed by C for the following reasons

Because the carbon atom is in the second period of the periodic table, the fourth main group, the outermost four electrons, it is not easy to lose these four electrons, and it is not easy to get the electrons supplied by other atoms, so when the carbon atom is combined with other atoms, it often adopts the form of covalent bonds, and the form of single bonds, double bonds, and triple bonds is often used between carbon and carbon in the form of long chains or rings, and branches can be formed in the long chains, and different compounds can be formed due to the different positions of the branches; Many compounds can be produced from adjacent edges and junctions between rings and rings; In addition to carbon-hydrogen elements, oxygen, nitrogen, sulfur, halogen, phosphorus and other elements are involved in it, forming many derivatives of hydrocarbons; It can also be polymerized into polymer compounds, such as sugars, proteins, etc., so there are many types of organic matter. Silicon with the same main group of carbon also has similar properties, but not many have been found so far, germanium and tin are metals, of course, there is no such property.

The fundamental reason is that there are 4 electrons in the outermost electron shell outside the nucleus of the C atom, and it is not easy to gain or lose electrons. In the formation of compounds, C atoms, or between C atoms and other atoms and atomic groups, can be connected to each other by single, double and triple bonds, and the connection form can be straight chains or branched chains.

The main component of organic matter is carbon, and the carbon atoms of organic compounds are very strong in binding and can be combined with each other to form carbon chains or carbon rings. The number of carbon atoms can be one, thousands, tens of thousands, and many organic polymer compounds (polymers) can even have hundreds of thousands of carbon atoms. In addition, isomerism is very common in organic compounds, which is one of the reasons for the large number of organic compounds.

1.Because carbon can form up to four covalent bonds, oxygen can only form two.

There are millions of compounds composed of carbon and hydrogen alone (alkanes, olefins, diolefins, alkynes, benzene and congeners, etc.), but only composed of oxygen and hydrogen are sullen water and hydrogen peroxide (what superoxide acid does not know exists).

2.Carbon can be formed by single, double, and triple bonds to form carbon chains, and the shield makes carbon rings.

3.Organic compounds are generally isomerized, for example, the structure of ethanol is C2H5OH, but dimethyl ether CH3OCH3 is also 2C, 6H, 1O, and acetic acid CH3COOH It has an isomer of methyl formate HCOOCH3

Elements A and C are essential elements for the composition of various organic compounds, and A is wrong;

B. Regardless of the fresh weight or dry weight of the cell, the contents of C, H, O, and N are the largest, and B is correct;

c. Ribose is a monosaccharide and does not contain phosphorus, and c. is wrong;

d. The types of chemical elements contained in different organisms are basically the same, and the content varies greatly

Organic matter must contain carbon elements, but compounds that contain carbon are not necessarily organic matter.

Carbon-free compounds like NaCl, H2SO4 and NaOH are called inorganic compounds, while a few carbon-containing compounds such as CO, CO2 and CACO3 are also regarded as inorganic compounds although they contain carbon. Organic matter must contain elemental carbon, but compounds that contain elemental carbon are not necessarily organic. Compounds that contain carbon but are not organic mainly include:

Carbon oxides, carbonic acid, carbonates, and bicarbonates.