Which of the following statements about intangible assets are correct? 1 If certain criteria are met, research expenditure must be recognised as an intangible asset. 2 The notes to the financial statements should disclose the gross carrying amount and the accumulated amortisation at the beginning and the end of the period for each class of intangible asset. 3 Intangible assets must be amortised over their useful life.
选项：

A:2 and 3 only ;
B:1 and 3 only ;
C:1 and 2 only ;
D:All three statements are correct