快把大衣穿穿！When is it wrong? In our book under 改錯句 there is the following exercise:



  外邊很冷，快把大衣穿穿！


I assume they consider it wrong because the object is not definite. Is that so, or is there any other reason?

If the context makes it clear that we are talking about a specific 大衣，would the sentence be ok, or do I absolutely need to grammatically express the definite nature by


  那件大衣/你的大衣/爸爸送給你的大衣⋯?


Edit: 

according to our book, reduplication of the verb makes the predicate complex, fulfilling the requirement for 把字句。 The example given is: 把桌子擦擦。
Ludi wrote:


  according to our book, reduplication of the verb makes the predicate complex, fulfilling the requirement for (把)字句


Reduplication of verb imply the verb is in 'a slight degree', 'a casual manner' or 'tentative manner'

Examples:

吃 = eat

吃吃 =  (slightly/ casually) eat

试 = try

试试 = (slightly/ tentatively) try

The first part of the sentence '外邊很冷' is a reason; the second part of the sentence '快把大衣穿穿 is a request/ command, you can switch the positions of the 'request/ command' and the 'reason' and the meaning would be the same. '快把大衣穿穿, (because) 外邊很冷'

Since this sentence request/ command  the object to do something definite, it shouldn't be in reduplication form that implies it is in 'slight', 'casual' or 'tentatively' manner

user3a is correct:


  外邊很冷，快把大衣「穿上」


把 is not an important factor in choosing reduplicate the verb or not.
You shouldn't  reduplicate 穿 in "外邊很冷，快穿上大衣" neither.