Which of the following elements is a metalloid?

Which of the following is the correct order of gradually decreasing basic nature of the oxides?

Which one of the following is most basic?

Given below are two statements:
Statement $I$ : Both metal and non-metal exist in $p$ and $d-$block elements.
Statement $II$ : Non-metals have higher ionisation enthalpy and higher electronegativity than the metals.
In the light of the above statements,choose the most appropriate answer from the option given below:

Arrange the acids $H_2SO_4$,$H_3PO_4$,and $HClO_3$ in the decreasing order of their acidic strength.

Given below are the oxides:
$Na_{2}O, As_{2}O_{3}, N_{2}O, NO$ and $Cl_{2}O_{7}$
Number of amphoteric oxides is ..... .