The paragraph below describes the limitations and suggestions for future direction of a study looking at the production of graphene layers. Complete the paragraph using the words and phrases in the box.

The study (1)____________that it is possible to produce large-area graphene films using a solid-phase-based method. It is (2)__ __________that this research can (3)____________a basis for further studies into graphene synthesis. One limitation of the present research is that the (4)____________ of the study did not (5)____________us to investigate the differences between using 6H-SiC and 3C-SiC/Si substrates. (6)____________this limitation, we do not know if this method is selective for the type of SiC substrate. In addition, the current study did not investigate a range of heating rates. It is possible that lower temperatures could be used if the process were lengthened. This is a (7)____________limitation of the study and (8) __ _________ further research questions related to the possibility of optimising processing conditions to better control graphene production.