Which of the following, when simplified, reduces to unity?

1   log10⁡102⋅log10⁡(10×2)+log10⁡22 =1−log10⁡21+log10⁡2+log10⁡22=1 (2)   log⁡22×3log⁡(48/4)=13   −log5⁡log3⁡91/10=−log5⁡log3⁡31/5=−log5⁡(1/5)=1 (4)   16log32⁡6427=16log32⁡32−6=−1