Shortly after implantation the embryo gastrulates (within 3 days) maternal blood sinuses bathe the inner cell mass myometrial cells cover and seal off the blastocyst the trophoblast forms two distinct layers

The correct answer is the trophoblast forms two distinct layers.

Under usual conditions, fertilization takes place in one of the fallopian tubes, then the fertilized egg starts to produce its path towards the uterus. By about the fifth day of conception, the embryo ultimately reaches the uterus and gets the implant in the uterine lining or endometrium.

During week II of implantation, the trophoblast layer gets involved by combining with the uterine wall, and during this time the layer of trophoblast differentiates and proliferates into two different layers, that is, cytotrophoblast and syncytiotrophoblast.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

in addition to spreading humanist ideas, erasmus has contributed to criticism of corruption in the church.