निम्नलिखित में से कौन सा घटक कांच को अदम्य (infusible) बनाता है और इसे अग्नि-प्रतिरोधी (fire-resistant) बनाता है?

Which of the following artificial stones is produced by moulding a mixture of iron slag and Portland cement?

Enamel paint is generally prepared by adding:

Dorry's testing machine is used for which test on building stones?