S1 cell and human reproduction

help me fill in the bank
? mean me unkmow
1.? occurs when a sperm and egg join togeter.
2.Fertilization usually occurs in the ?.
3.? is the eybryo attaches itself to the uterus lining.
4.Watery liquid protects the foetus from ?.
5.?,?,? and ? are exchanged through the placenta.
6.An absence of ? is the most obvious sign of pregnancy.
7A.How many sperms are involved? identical/non-identical twins
7B.How many eggs are involved? identical/non-identical twins
7C.Do the twins have same genetic material identical/non-identical twins
8.? and ? are one of the signs of sexful maturity in girls and boys respectively