Note the word 'NOT' in the question. In order for a competitive tender to be successful, there should be a clear specification in place (i.e. you need to know what you want, in order for suppliers to bid for it). Competitive tendering should also only be used for high value purchases; it's time consuming to do, so you wouldn't do it for low value items such as pens for the office. Therefore the correct answer to this question is 'items are of low value' and 'there isn't a clear specification'. There's a useful table on p.73 of when you would and wouldn't use a competitive tender.