In SLSH ___________ combine two nouns or noun phrases joined by "and" to connect related or opposing subjects.

The Correct answer is Compound Headings.

Key Points

• A phrase heading consists of two or more words representing the subject of a document. 
• The different types of phrase headings as recognized in SLSH are discussed below

Compound Headings

• These combine two nouns or noun phrases joined by "and" to connect related or opposing subjects.
• Examples include:
• Bow and Arrow
• Cities and Towns
• Religion and Science
• Belief and Doubt

Adjectival Headings:

• An adjective is used to qualify a noun, expressing a specific concept.
• Examples include:
• American literature
• Electrical engineering
• Tropical fish
• Previously, adjectival headings were often inverted (e.g., Psychology, Religious), but this practice has largely been replaced by direct ordering, except in cases like battles or states.
• A reference from the older inverted form is added when necessary.

Prepositional Phrase Headings:

• These express relationships between concepts using prepositions.
• Examples include:
• Freedom of information
• Electricity in agriculture