The correct option is C Merchandise
A synonym is a word that is similar in meaning to another.
The given word 'goods' refers to any possessions or items, generally with reference to trade and commerce. For example, 'The goods were sent by air mail.' ('Good is a quality whereas 'goods' is a commodity.)
From the options, 'merchandise' refers to commodities or goods that are bought or sold. Consider the sentence: The merchandise was sent by air mail. Hence it is synonymous in meaning and option C is correct.
'Quality' refers to nature, character or condition of something, for example, 'This place is famous for its quality of ingredients.' It does not mean the same as 'goods'. (The former is an abstract noun whereas the latter is a concrete noun.) Hence option A is incorrect.
'Transport' means 'to carry from one place to another'; goods are transported, but goods don't mean the same as 'transport', the latter being an action. Hence option B is incorrect.
'Upright' means 'honourable or honest', for example, 'an upright member of the society'. It refers to a quality and does not refer to 'goods', hence option D is incorrect.