Examine carefully the extract below which has been taken from the same text you have just read (Marshall, Gamble, Roe & Dupplaw 2002). It contains three statements. Try answering the questions that follow:
'The artefacts included in this study so far were those collected by Louis Leakey during 1931 and 1935, which are held by the National Museum of Tanzania in Dar es Salaam. The more substantial collections generated during later work, in many cases during controlled excavations, are now held in Nairobi, Kenya. This means that many of the assemblages included in this study are disappointingly small'
(extract from Marshall, Gamble, Roe & Dupplaw 2002)
In your opinion, how certain are the authors of these three statements?