Answer: A) Diamond Explanation: Diamond is the hardest substance available on Earth. Diamond is the hardest substance available on Earth due to the giant molecular structure of diamond in which each carbon atom is covalently bonded to four other carbon atoms. A covalent bond is very strong and requires a large amount of energy to break itself, and diamond has many covalent bonds.

Answer: C) the chemical properties of their R groups Explanation: Amino acids are organic compounds containing amine (-NH2) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid.   Depending on the nature of the side chain groups, three classes of aminoacids can e distinguished: 1. Amino acids with H ond donor and acceptor groups. Histidine, lysine, aspartic acid, threonine,... 2. Amino acids with donor grups only. Arginine, tryptophan and cysteine. 3. Amino acids with acceptor groups only. Asparagine and glutamine.

Answer: C) 9 & 21 Explanation: Let the two numbers be x and y Given x : y = 3 : 7 .....(1) Now, x+6 : y+6 = 5 : 9 .....(2) From (1), x = 3y/7 From (2), 5y - 9x = 24 => 5y - 9(3y/7) = 24 => y = 21 => From(1), x = 9 Hence, the two numbers be 9 and 21

Answer: D) Nucleus Explanation: In the cell, transcription occurs in the nucleus in the presence of DNA. Terms transcription and translation in biology are generally related to the DNA and its properties. Human cells replicate. In order to do that, they have to produce the same constituents for the new cell that is to be made. The only way to do that is by producing proteins. The proteins are produced in the process that is called protein synthesis. The first step is in the nucleus where a particular gene is being expressed so it enables all protein factors to come and to replicate that part of a chromosome. This is finished when mRNA, the same single-stranded genetic code of a particular gene, is formed. This is transcription. Right after that, the mRNA enters the cytoplasm through nuclear pores. There, it could be translated into proteins by ribosomes. This process is called translation.   Hence, Transcription occurs in the nucleus, whereas translation occurs in the cytoplasm.