What are layers? why would a layer be used?

What kind of software users of all skill levels create web pages that include graphics, video, audio, animation, and other special effects? website authoring website software website publishing website editing

Shown below is the start of a coding region within the fist exon of a gene. 5'--3' 3'--5' how many cas9 pam sequences are present?

Awell-diversified portfolio needs about 20-25 stocks from different categories is this true or false?