Kết luận nào đúng về số thực $a$ nếu ${\left( {\dfrac{1}{a}} \right)^{ - 0,2}} < {a^2}$

$f\left( 0 \right) < 5$

$f\left( 2 \right) \geqslant 5$ 

$f\left( 1 \right) = 5$      

$f\left( 0 \right) = 5$

$a > 1$

$0 < a < 1$

$a \ge 1$        

$a > 0$ 

$\mathop {\lim }\limits_{x \to 0} \dfrac{{\ln \left( {1 + x} \right)}}{x} = 1$

$\mathop {\lim }\limits_{x \to 0} \dfrac{{\ln \left( {1 - x} \right)}}{x} = 1$

$\mathop {\lim }\limits_{x \to 0} \dfrac{{\ln x}}{x} = 1$

$\mathop {\lim }\limits_{x \to 0} \dfrac{{\ln \left( {1 + x} \right)}}{{1 + x}} = 1$

$R$ 

$R\backslash \left\{ 0 \right\}$ 

$\left( { - \infty ;0} \right)$ 

$\left( {0; + \infty } \right)$ 

$\dfrac{{3{a^3}\sqrt 3 }}{8}$

$\dfrac{{{a^3}\sqrt 3 }}{8}$           

$\dfrac{{3{a^3}}}{8}$        

$\dfrac{{{a^3}}}{8}$

$2\log a + \log b$

$\log a + 2\log b$

$2\left( {\log a + \log b} \right)$

$\log a + \dfrac{1}{2}\log b$

$a > 0$ 

$a = 0$

$a < 0$ 

$a \ne 0$