Cloning has two major uses. First, gardeners use it to produce large     1     (quantity) of plants for sale. Second, it is valuable for research on new plant species and for medical research on animals. Cloning plants is fairly straightforward, while cloning animals is much     2     (complicated) and difficult. Over the years, many scientists failed in their attempts to clone animals, but their determination and     3     (patient) paid off in 1996 with a breakthrough-the cloning of Dolly the sheep.

Tu Youyou was awarded the Nobel Prize in 2015 for her research,     1     led to the discovery of artemisinin. Artemisinin has saved a large number of lives since it was discovered. After     2     (graduate) from university, Tu Youyou worked at the China Academy of Traditional Chinese Medicine. In 1967, Tu Youyou     3     (choose) as a researcher of a team of scientists with     4     purpose of discovering a new treatment for malaria.

To truly understand our planet, we must explore the oceans..., but sea exploration is important for our future. For example, scientific research ships can help     1         2         3     such as climate change.

Of course, there are still environmental risks. However, these should be balanced with economic needs. Hopefully, as technology improves, we may have more     4         5         6     this balance.