Which are the special proteins in muscles that contract and relax to cause movement?

 

The marrow cavity is also known as the medullary cavity. It is the central cavity of bone shafts where adipose tissue is stored. It is lined with a thin, vascular membrane called endosteum.

The plant cell organelles, "The power house of the cell" mitochondria and the chloroplasts contains their own DNA and ribosomes.

Protists are eukaryotic organisms that cannot be classified as a plant, animal, or fungus. They are mostly unicellular, but some, like algae, are multicellular.

Kelp, or 'seaweed,' is a large multicellular protist that provides food, shelter, and oxygen for numerous underwater ecosystems.

Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products.

DNA is not a single stranded and does not have amino acids. Hence options, b & C are eiminated. Dna is a double helix structure containing nucleobase—either cytosine (C), guanine (G), adenine (A), or thymine (T)—as well as a monosaccharide sugar called deoxyribose and a phosphate group. 

In the above options, sperms are the haploid cells. In humans, haploid cells are those have only half the number of usual number of chromosomes. Sperm, gamates and egg cells are the haploid cells examples.