put have has or had where appropriate in the following sentence, Exam malpracticesbecome a serious issue​

What are the primary responsibilities of a chemical engineer involved in "r& d"? develop large scale manufacturing operations discover new products and processes training of new chemists determine products needed by consumers

Acandle’s wick is the fabric string that holds the flame, and it burns down at a constant slow pace when the candle is lit. the wick is usually surrounded by wax. which is the most important property of covalent compounds that makes them useful for making candle wax? a low boiling point a low melting point a high boiling point a high melting point

Which one of the following bonds would you expect to be the most polar? a) b–h b) n–h c) p–h d) al–h e) c–h