Colour of rose petals is due to water-soluble pigments present in:
A. Cytoplasm
B. Intercellular spaces
C. Nucleus
D. Vacuoles

Hint: The colour present in rose petals is due to the presence of anthocyanin which is a pigment. These are the common pigments present in plants which are water-soluble in nature.

Complete step by step answer: Anthocyanins are located in the cell vacuoles and are coloured differently as red, purple or blue. The colour of the pigment depends on the pH. The major pigments responsible for colouration are anthocyanin and carotenoids. These pigments determine the colour of the petals and are dependent on a variety of conditions such as temperature. Considering the other given options:
A. Cytoplasm: The major function of the cytoplasm is to act as a medium for suspension of all the organelles inside the cell. It also acts as a buffer in maintaining the pH of the cell and also as a protection for the genetic material enclosed within. The vacuoles containing anthocyanin pigments are suspended in the cytoplasm.
B. Intercellular spaces: These are also known as pore or air spaces and exist between adjacent cells. The main functions of these spaces are that it helps in the exchange of gases and water transport between the cells.
C. Nucleus: Nucleus is a vital organelle in the plant cell. It controls and regulates all the functions of the cell. It is the main location for the DNA replication process and contains the genetic material.
Therefore, the correct answer is option D.

Note: Vacuoles perform multiple vital functions in plant cells. They act as a reservoir to ions and various metabolites including different pigments. They participate in ensuring stiffness and facilitates the growth of the cell. Also functions as a storage area for reserved carbohydrates and proteins.