Answer:
Pteridophytes are vascular plants but they do not produce flowers and seeds which mean their source of reproduction is unknown or hidden.
On the contrary, Spermatophytes as the name indicates, are seed bearing plants. They produced seeds and flowers. Examples are flowering plants, cactus, leather flower, buttercup and may more.
Explanation:
Correct answer - Tetrahedral, planar or flat.
Why? - When carbon forms single bonds with other atoms, the shape is tetrahedral. When two carbon atoms form a double bond, the shape is planar, or flat. Single bonds, like those found in ethane, are able to rotate.
Ductility is a physical property.
A physical property of a material is a property that can be measured or observed without changing the composition of the material.
In this case ductility is a physical property. It is defined as the property of a material associated with the ability to be drawn or stretched into a wire without breaking. The chemical identity of the material is not affected, that is it does not change.
Example of ductile materials include gold, silver, copper, erbium, terbium and samarium.
Other examples of physical properties are:
1. Solubility
2. Melting point.
3. Boiling point.
4. Color
5. Density.
Describe<span> the physical </span>properties of the Sun<span> (sunspot cycles, solar flares, prominences, layers of the </span>Sun<span>, coronal mass ejections, and nuclear reactions) and the impact of the </span>Sun<span> as the main source of external energy for the Earth</span>
