Questions

An up - selling is getting the customer to spend more money, buy a more expensive model of the same type of product, or add features or warranties that relate to the product viewed or purchased. 

A cross - sell is to get the customer to spend more money by adding more products from other categories than the product being viewed or purchased. 

Allotropes are the different physical forms of an element. Here in the given options, diamond and graphite are the pair of allotropes of carbon.

Some more examples are Molecular oxygen and ozone are pair of allotropes, Black and red phosphorous are also pairs of allotropes.

Robert Brown, Scottish botanist, Discovered The Nucleus of a Cell in 1831, London. When Brown was studying orchids under microscope when he observed an opaque area, which he called the "Areola" or "Nucleus", in the cells of the flower's outer layer.

The nucleus was also described by Franz Bauer in 1804 but in detail Robert Brown made it in 1831.

Capillaries Tiny blood vessels connecting arteries to veins. These blood vessels carry oxygen

and nutrients to individual cells. Capillaries are the smallest blood vessels in the body, and have

walls only one or two cells thick. (Their diameter is 5 to 10 micrometers, or 5 to 10 millionths of

a meter.)

Capillaries connect arterioles and venules, which are the smaller extensions of the larger arteries and veins.