With reference to the latest developments in stem cell research consider the following statements
1. The only source of human stem cells are the empryos at blastocyst stage.
2. The stem cells can be derived without causing destruction to blastocysts.
3. The stem cells can regnerate themselves in vitro virtually farever.
4. Indian research centres also created a few cell lines which can be developed into many types of tissues. Which of the statement ate coorect?