________ is a useful method of asexual reproduction for propagating hard-to-root plants.

a. grafting

b. layering

c. cuttings

d. budding

Asexual reproduction is a type of reproduction that produces genetically identical offsprings without the fusion of male and female gametes.

Asexual reproduction in plants includes budding, fragmentation, vegetative propagation, and spore formation. These methods eliminate the usage of flowers for reproduction. Asexual reproduction produces plants that survive in stable environments.

Let's take a look at each choice one by one:

Budding

Budding is a type of asexual reproduction in which new plants arise from an offshoot known as bud. A bud is formed through the division of cells in a single region. Potato is an example of plant where new individuals can be produced through budding. Potatoes develop number of little offshoots called "eyes", when kept aside for a long time. Each of these offshoots can be planted and will mature into new potato plants.

Layering

It is a technique of asexual reproduction, where a plant's stem is lowered and covered in soil. The stems while still attached to the plant and covered in soil, grows roots and then eventually detaches from the parent plant to form a new independent plant.

Cutting

• This asexual method involves cutting a part of a plant along with the node and burying it in the soil.
• The cutting is watered on a regular basis, which eventually grows to form a new plant.
• This method is considered to be the most cost-effective method of vegetative propagation.

Grafting is a type of vegetative propagation that is done artificially.

• In this method two sections of two different plants are joined together and grown as a together as a single plant.
• The part of the plant that is rooted is called the stock and other part which is planted on to the stock is called a scion.