Identify the reagents $X, Y, Z$ for the following dehydration reactions of alcohols:
$CH_3-CH_2-OH \xrightarrow{X} CH_2=CH_2 + H_2O$
$CH_3-CH(OH)-CH_3 \xrightarrow{Y} CH_3-CH=CH_2 + H_2O$
$(CH_3)_3C-OH \xrightarrow{Z} (CH_3)_2C=CH_2 + H_2O$

• A

  $X$	$Y$	$Z$
  $H_2SO_4, 443 \ K$	$85 \% \ H_3PO_4, 440 \ K$	$20 \% \ H_3PO_4, 358 \ K$

• B

  $X$	$Y$	$Z$
  $85 \% \ H_3PO_4, 440 \ K$	$H_2SO_4, 443 \ K$	$20 \% \ H_3PO_4, 358 \ K$

• C

  $X$	$Y$	$Z$
  $20 \% \ H_3PO_4, 358 \ K$	$H_2SO_4, 443 \ K$	$85 \% \ H_3PO_4, 440 \ K$

• D

  $X$	$Y$	$Z$
  $H_2SO_4, 443 \ K$	$20 \% \ H_3PO_4, 358 \ K$	$85 \% \ H_3PO_4, 440 \ K$