There are two main types of chromosomal disorders, those that take place on the 21st pair of chromosomes and those that

Down syndrome and Alzheimer's disease.

Down syndrome is a chromosomal disorder which is caused by the presence of extra copy of chromosome  21. Therefore also called as Trisomy 21.

Alzheimer's disease is a most common form of dementia(reduction in brain functioning). It is caused by mutation in single gene APP (Amyloid Precursor Protein) present on chromosomer 21.

correct answer: false

while planning water activities, it is very important to consider the weather, because if we do not plan and are going for a surf, then it might be that the hurricane came and drown us or may carry us to long distance from where we can not come back. there are many reasons to take information about the weather when we are planning any water activities.

hence, the correct answer would be false.