5) Assinale com X os nomes de variáveis válidos:

1.(x)abc                              2.(  )3abc                          3.(x)a                       4.(  )123ª

5.(  ) -a                               6.(x)acd1                          7.(  )-_ad                  8.(  )A&a

9.(x) prim-nom                  10.(x) A123                        11.(x)Aa                   12.(x) prim_nom

13.(  ) ABC  DE                14.(  )etc.                            15.(x) E                    16.(  )"nome"