1. ____________ is a structure that can protect a plant cell.
2. Single celled living things usually reproduce by _____________.
3. During sexual intercourse, the penis of the male is put into the vagina of the female. A liquid containing sperms is released. Sperms swim from the vagina to the __________
and then reach the ____________________________. If an egg is present, a sperm will join with it. This process is called ____________.
更新1:
4.A foetus is joined to the placenta by the _________. The foetus obtains __________________ and ________ from the placenta. 5.AIDS can be infected via _____________, ________________________ and from the mother to the developing foetus during pregnancy.
更新2:
6.Sperms are produced by tests and are transport to the urethre via ___________________.
