Step 1: Understand the passage content.
The passage explains that social media platforms have both positive and negative effects. On the positive side, they enable instant connectivity and sharing of information. On the negative side, they have been criticized for spreading misinformation and causing mental health problems like anxiety and depression.
Step 2: Identify the criticism.
Among the criticisms mentioned, "spreading misinformation" is explicitly stated, which matches option (C).
Step 3: Evaluate other option.
(A) They improve mental health — The passage states the opposite by mentioning mental health issues.
(B) They reduce connectivity — The passage says they enable instant connectivity.
(D) They prevent information sharing — The passage states they enable information sharing.
Hence, the correct answer is option (C) They contribute to spreading misinformation.