Which pair of elements would be expected to form an ionic bond? a. nitrogen & oxygen b. lithium & fluorine c. carbon & hydrogen d. silicon & chlorine

lithium and fluorine  

Lithium donates an electron to fluorine and make the fluorine with a negative charge and a full outer shell. Lithium consequently get a positive charge and a full outer shell. They then are attracted to each other an form a giant ionic lattice.  

Carbon and hydrogen are organic so they don't  

Nitrogen and Oxygen are also organic.  

Chlorine can form ions but not with silicon

B. lithium & fluorine

"do a testcross with a homozygous recessive plant."

this is a good question! i'll do some research and come back when i have the answer!