HTTP is stateless, meaning it does not maintain session information between requests. Each request is independent  .

HTTP follows a request–response model, where the client initiates a request and the server responds. That means communication is always client → server → client, not simultaneous in both directions.

Although newer versions (like HTTP/1.1 with pipelining or HTTP/2 multiplexing) allow more efficient handling, HTTP is still fundamentally half-duplex—it’s not full duplex because only one side can actively send at a time.

Why not the other options?

(A) Stateful – Incorrect. HTTP doesn’t preserve state between requests  .

(C) Bidirectional – Incorrect. While data does go back and forth, it's not spontaneous from both ends; the server only responds after a request.

(D) Full duplex– Incorrect. Only one side transmits at a time; true full duplex (simultaneous two-way communication) is seen in protocols like WebSocket, not HTTP.

So, HTTP is best described as a stateless, unidirectional (half-duplex) request–response protocol.

Answer: (B) unidirectional

All the listed services — Twitter, Skype, and Gmail — are built on cloud-computing technology. Here's how:

• Twitter: Uses cloud infrastructure to scale, store tweets, and manage millions of concurrent users.
• Skype: Operates over the internet using cloud servers for voice/video calls and messaging.
• Gmail: A Google service entirely cloud-based, offering email access from anywhere via web and mobile apps.

These services rely on cloud computing for scalability, availability, storage, and performance.

Moderate anaerobes (also called microaerophiles) require low levels of oxygen, typically around 2–8%, for their growth.

• They cannot grow in atmospheric oxygen (~21%) but need some oxygen to survive.

Why other options are incorrect:

• (A) 0%: This corresponds to strict anaerobes that require no oxygen.
• (B) < 0.5%: Too low for moderate anaerobes.
• (D) 5 – 10%: Slightly higher, but generally microaerophiles prefer 2–8%.

Final Answer: (C) 2 – 8%

Aspartic acid (Asp) has a carboxyl group in its side chain that loses a proton at physiological pH (~7), making it negatively charged.

Why others are incorrect:

• (B) Histidine (His): Side chain is positively charged or neutral around pH 7 because its imidazole group has a pKa close to physiological pH but usually not negatively charged.
• (C) Tryptophan (Trp): Nonpolar, uncharged side chain.
• (D) Cysteine (Cys): Has a thiol group, which is mostly neutral at physiological pH (can be negatively charged but only under more alkaline conditions).

Final Answer: (A) Asp