How has the artificial manipulation of plasmids been used for technological applications? ?

Plasmids refer to a small molecule of DNA found within a cell that physically gets distinguished from a chromosomal DNA and possesses the tendency to replicate autonomously. The plasmids are generally found in bacterial cells in the form of small circular, double-stranded DNA. The plasmids are used commonly by scientists as the tools to manipulate and clone genes. The plasmids, which are used for these specific objectives are known as vectors.  

The administration of the desired gene from one species to another has become possible with the help of plasmids. Thus, plasmids help in performing genetic modification. The procedure by which genetic makeup of a species is changed is called genetic engineering or genetic modification.  

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.