Math Help - Linearly Dependent

1. Linearly Dependent

I am having trouble justifying the following:

Explain why the column vectors of a 3 x 4 matrix form a linearly dependent set (assuming all matrix entries are distinct)

Any help would be appreciated,

Thanks

2. $If~A\in R^{3\times 4}\rightarrow rank(A)\leq 3\rightarrow$There are at most three independent vectors in columns, so there must be dependent of 4 columns