The basic unit of life is cell(s).
From the deepest to most superficial: pia mater, arahnoid, dura mater
An estuary is an area where a freshwater river or stream meets the ocean. In estuaries, The salty ocean mixes with a fresh water river, resulting in brackish water. Brackish water is someone salty, but not as salty as the ocean. An estuary may also be called a bay, lagoon, sound, or slough.
The correct answer is: The synaptonemal complex.
Non-sister chromatids are chromatids from two homologous chromosomes. In prophase I of meiosis two homologous chromosomes pair and this pairing is called synapsis. This allows possible crossing over to occur. Two non-sister chromatids are connected in synapsis by a protein-RNA complex called the synaptonemal complex.
Crossing-over or the physical exchange of chromosome parts might occur and bring to genetic recombination. The sites of crossing-over between nonsister chromatids and are called chiasmata.