Rule 1: 1. Persons and things once more
Plurals of persons take plural demonstratives, adjectives, pronouns and verbs; plurals of things take the feminine singular. Watch the pairs below.
هٰؤُلَاءِ التَّلَامِيذُ مُجْتَهِدُونَ وَأُولٰئِكَ التَّلَامِيذُ كُسَالَى.
hāʾulāʾi-t-talāmīdhu mujtahidūna wa-ulāʾika-t-talāmīdhu kusālā
These pupils are diligent and those pupils are lazy.
Persons: هٰؤُلَاءِ / أُولٰئِكَ and plural adjectives.
هٰذِهِ الدَّفَاتِرُ رَخِيصَةٌ وَتِلْكَ الدَّفَاتِرُ غَالِيَةٌ.
hādhihi-d-dafātiru rakhīṣatun wa-tilka-d-dafātiru ghāliyatun
These notebooks are cheap and those notebooks are expensive.
Things: هٰذِهِ / تِلْكَ and feminine singular adjectives.
اَلتَّلَامِيذُ رَجَعُوا مِنَ الْمَدْرَسَةِ.
at-talāmīdhu rajaʿū mina-l-madrasati
The pupils came back from school.
Plural verb after a plural subject of persons.
اَلْخُطُوطُ الَّتِي رَسَمَهَا مُسْتَقِيمَةٌ.
al-khuṭūṭu-llatī rasamahā mustaqīmatun
The lines that he drew are straight.
Things: relative اَلَّتِي, suffix ـهَا, adjective feminine singular.