Answer:
The answer is hormones.
Explanation:
Two of the main systems that control almost every action in our body are our nervous system and endocrine system which have to have inner communications and communication with our brain.
As stated in the question, nervous system uses neurotransmitters for communication which are chemicals released by neurons to generate electrical signals that make the communication possible.
The main mean of communication that our endocrine system uses is substances that are called "Hormones" which are produced by certain glands and organs in our body and are usually released into our bloodstream to effect the functions of other organs and our body. Hormones can be used for both communication of the endocrine system itself and for the communication of other organs and our brain.
I hope this answer helps.
Answer
Correct answer is :It has two elements
Explanation
A binary compound is a compound that is made up of two of the elements in the periodic table. Some examples of binary compounds are 
and 
. This means that a binary compound can have more than 2 atoms as in the case of hydrogen oxide. Some binary compounds are ionic as in the case of sodium chloride.This shows that they do not necessarily have to have covalent bonds. This also rules out the possibility that they may always have double bonds as ionic compounds are bound together by ionic bonds. The only thing that will always be true of binary compounds is that they will always have 2 elements.
The could have snuck away on a ship, as they are very sneaky
B. long fibres in celery
(I've done an experiment in my science class once on xylem tissue on celery)
