Which of the following are proper units of mass in the metric system ounce kilogram meter milligram

kilogram and milligram are proper units of mass in the metric system . Anything with the suffix -gram is a mass measurement  Hope this helps!

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< coa = 150 ( given)

as ba and bc are tangents

so oc and oa is perpendicular to cb and ab respectively because in circle normal passes through centre

so in quadrilateral oabc

< coa + < oab + < ocb + < abc = 360

150 +90+90 + < abc = 360

330 + < abc = 360

< abc = 360 -330 = 30

so < abc = 30

⭐dhruv⭐