a. These cells have formed mesoglea.
- Mesoglea is the amorphous, acellular layer in cnidarians that separates the ectodrerm and the endoderm.
- The mesoglea is referred to as the hydrostatic skeleton in cnidarians such as jelly fish.
- The mesoglea, although supplied with muscles and nerves, is completely composed of water.
The correct answer is "mutations in the lac operon or in the promoter region".
The lac operon es a series of genes that are translated and expressed simultaneously, allowing the cell to metabolize lactose when glucose is absent. The E.coli cultures that failed to grow in the presence of only lactose, could have a mutation that affects the lac operon. This mutation could be present in the promoter region or in the lac operon itself, which will result in the absence of lac operon transcription or in the transcription of one or more non active protein, respectively.
The answer is Protons and neutrons.