The DHCP scope defines the range of IP addresses that the DHCP server can assign to the devices on the network.
In this scenario, the network technician installed 35 additional workstations, which increased the demand for IP addresses on the network.
If the DHCP scope is not large enough to accommodate the new workstations, some of them will not be able to obtain an IP address from the DHCP server and will not be able to access network resources.
This would also affect the original workstations that were offline when the new workstations were turned on, as they would have to renew their IP addresses from the DHCP server when they come online.
To solve this problem, the network technician should check the DHCP scope and either increase the range of IP addresses or create a new scope for the additional workstations.
Incorrect VLAN setting, improper NIC setting, and duplicate IP address are not the most likely causes of this issue, as they would affect individual workstations or specific segments of the network, not the entire network. Reference:
[CompTIA Network+ N10-008 Study Guide], Chapter 2: Network Devices and Technologies, Section 2.2: Configure and Support IPv4 and IPv6 Addressing, p. 67-68
[Professor Messer's CompTIA N10-008 Network+ Course Notes], Section 1.3: Network Services, p. 13 Network+ N10-008 Practice Test | CertBlaster, Question 1

show interface is a command-line tool that displays information about the status, configuration, and statistics of an interface on a network device. A technician can use show interface to determine where the incident is occurring in a network by checking the uplink status, speed, duplex mode, errors, collisions, and other parameters of each interface. References: https://www.comptia.org/blog/what-is-show-interface